diff --git a/projects/packages/jetpack-mu-wpcom/changelog/cm-841-surface-login-requirement b/projects/packages/jetpack-mu-wpcom/changelog/cm-841-surface-login-requirement
new file mode 100644
index 000000000000..ab726c9841ed
--- /dev/null
+++ b/projects/packages/jetpack-mu-wpcom/changelog/cm-841-surface-login-requirement
@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+Verbum Comments: explain why commenting is unavailable when login is required but the login options cannot be shown, instead of offering a form that will be rejected.
diff --git a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/class-verbum-comments.php b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/class-verbum-comments.php
index 59a7025e7b0a..99e2ead82116 100644
--- a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/class-verbum-comments.php
+++ b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/class-verbum-comments.php
@@ -237,6 +237,7 @@ public function enqueue_assets() {
 					/* translators: %s is the name of the provider (WordPress, Facebook, Twitter) */
 					'Logged in via %s'                   => __( 'Logged in via %s', 'jetpack-mu-wpcom' ),
 					'Log out'                            => __( 'Log out', 'jetpack-mu-wpcom' ),
+					'Your browser is blocking the cookies needed to log in and comment here. Allow cookies in your privacy settings, then reload the page.' => __( 'Your browser is blocking the cookies needed to log in and comment here. Allow cookies in your privacy settings, then reload the page.', 'jetpack-mu-wpcom' ),
 					'Email'                              => __( 'Email', 'jetpack-mu-wpcom' ),
 					'(Address never made public)'        => __( '(Address never made public)', 'jetpack-mu-wpcom'), // phpcs:ignore PEAR.Functions.FunctionCallSignature.SpaceBeforeCloseBracket
 					'Instantly'                          => __( 'Instantly', 'jetpack-mu-wpcom' ),
diff --git a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/components/logged-out.tsx b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/components/logged-out.tsx
index 1b96b5824aad..46e08490fa2a 100644
--- a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/components/logged-out.tsx
+++ b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/components/logged-out.tsx
@@ -10,7 +10,6 @@ import type { SocialServiceName } from '../hooks/useSocialLogin';
 const { mustLogIn, requireNameEmail, commentRegistration } = VerbumComments;
 interface LoggedOutProps {
 	login: ( service: SocialServiceName ) => void;
-	canWeAccessCookies: boolean;
 	loginWindow: Window | null;
 }
 
@@ -40,7 +39,7 @@ const getLoginCommentText = ( commentParent: Signal ) => {
 	return <span>{ defaultText }</span>;
 };
 
-export const LoggedOut = ( { login, canWeAccessCookies, loginWindow }: LoggedOutProps ) => {
+export const LoggedOut = ( { login, loginWindow }: LoggedOutProps ) => {
 	const [ activeService, setActiveService ] = useState( '' );
 	const closeLoginPopupService = requireNameEmail && ! mustLogIn ? 'mail' : '';
 
@@ -82,72 +81,83 @@ export const LoggedOut = ( { login, canWeAccessCookies, loginWindow }: LoggedOut
 		setActiveService( service );
 	};
 
-	const { commentParent } = useContext( VerbumSignals );
+	const { canAccessCookies, commentParent, isCommentBlocked } = useContext( VerbumSignals );
 
 	return (
 		<div className="verbum-subscriptions logged-out">
 			<div className="verbum-subscriptions__wrapper">
 				<div className="verbum-subscriptions__login">
-					{ canWeAccessCookies && (
-						<>
-							<div className="verbum-subscriptions__login-header">
-								{ getLoginCommentText( commentParent ) }
-							</div>
+					{ ( canAccessCookies || mustLogIn ) && (
+						<div className="verbum-subscriptions__login-header">
+							{ getLoginCommentText( commentParent ) }
+						</div>
+					) }
+					{ isCommentBlocked.value && (
+						<p className="verbum-subscriptions__cookie-notice" role="status">
+							{ translate(
+								'Your browser is blocking the cookies needed to log in and comment here. Allow cookies in your privacy settings, then reload the page.'
+							) }
+						</p>
+					) }
+					{ canAccessCookies && (
+						<div
+							className={ clsx( 'verbum-logins', {
+								'logging-in': activeService,
+							} ) }
+						>
 							<div
-								className={ clsx( 'verbum-logins', {
-									'logging-in': activeService,
+								className={ clsx( 'verbum-logins__social-buttons', {
+									'show-form-content': ! mustLogIn,
 								} ) }
 							>
-								<div
-									className={ clsx( 'verbum-logins__social-buttons', {
-										'show-form-content': ! mustLogIn,
-									} ) }
-								>
-									{ Object.entries( serviceData ).map( ( [ service, value ] ) => {
-										// Don't show mail login if "Users must be registered and logged in to comment" enabled.
-										if ( mustLogIn && service === 'mail' ) {
-											// eslint-disable-next-line array-callback-return
-											return;
-										}
-
-										return (
-											<button
-												aria-label={ value.name }
-												type="button"
-												key={ service }
-												onClick={ e => handleClick( e, service ) }
-												className={ clsx( 'social-button', service, {
-													active: service === activeService,
-												} ) }
-											>
-												<value.icon />
-											</button>
-										);
-									} ) }
-								</div>
-								{ [ 'wordpress', 'facebook' ].includes( activeService ) && (
-									<div
-										className={ clsx( 'verbum-login__social-loading', {
-											'must-login': mustLogIn,
-										} ) }
-									>
-										<p></p>
+								{ Object.entries( serviceData ).map( ( [ service, value ] ) => {
+									// Don't show mail login if "Users must be registered and logged in to comment" enabled.
+									if ( mustLogIn && service === 'mail' ) {
+										// eslint-disable-next-line array-callback-return
+										return;
+									}
+
+									return (
 										<button
+											aria-label={ value.name }
 											type="button"
-											className="components-button is-link"
-											onClick={ () => {
-												setActiveService( closeLoginPopupService );
-												loginWindow?.close();
-											} }
+											key={ service }
+											onClick={ e => handleClick( e, service ) }
+											className={ clsx( 'social-button', service, {
+												active: service === activeService,
+											} ) }
 										>
-											{ translate( 'Cancel' ) }
+											<value.icon />
 										</button>
-									</div>
-								) }
+									);
+								} ) }
 							</div>
-						</>
+							{ [ 'wordpress', 'facebook' ].includes( activeService ) && (
+								<div
+									className={ clsx( 'verbum-login__social-loading', {
+										'must-login': mustLogIn,
+									} ) }
+								>
+									<p></p>
+									<button
+										type="button"
+										className="components-button is-link"
+										onClick={ () => {
+											setActiveService( closeLoginPopupService );
+											loginWindow?.close();
+										} }
+									>
+										{ translate( 'Cancel' ) }
+									</button>
+								</div>
+							) }
+						</div>
 					) }
-					<EmailForm shouldShowEmailForm={ activeService === 'mail' || ! canWeAccessCookies } />
+					<EmailForm
+						shouldShowEmailForm={
+							activeService === 'mail' || ( ! canAccessCookies && ! mustLogIn )
+						}
+					/>
 				</div>
 			</div>
 		</div>
diff --git a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/index.tsx b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/index.tsx
index 02a37d8e6175..5c1fd42a33c8 100644
--- a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/index.tsx
+++ b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/index.tsx
@@ -12,12 +12,7 @@ import useFormMutations from './hooks/useFormMutations';
 import useSocialLogin from './hooks/useSocialLogin';
 import { translate } from './i18n';
 import { createSignals, VerbumSignals } from './state';
-import {
-	canWeAccessCookies,
-	setUserInfoCookie,
-	addWordPressDomain,
-	hasSubscriptionOptionsVisible,
-} from './utils';
+import { setUserInfoCookie, addWordPressDomain, hasSubscriptionOptionsVisible } from './utils';
 import type { VerbumAppProps } from './types';
 
 import './style.scss';
@@ -25,6 +20,7 @@ import './style.scss';
 const Verbum = ( { siteId, parentForm }: VerbumAppProps ) => {
 	const {
 		hasOpenedTrayOnce,
+		isCommentBlocked,
 		isEmptyComment,
 		isSavingComment,
 		isTrayOpen,
@@ -160,6 +156,11 @@ const Verbum = ( { siteId, parentForm }: VerbumAppProps ) => {
 	};
 
 	const handleCommentSubmit = async ( event: Event ) => {
+		if ( isCommentBlocked.value ) {
+			event.preventDefault();
+			return;
+		}
+
 		window.removeEventListener( 'beforeunload', handleBeforeUnload );
 		if ( userInfo.value?.service === 'guest' ) {
 			if ( shouldStoreEmailData.value ) {
@@ -226,11 +227,7 @@ const Verbum = ( { siteId, parentForm }: VerbumAppProps ) => {
 				{ userLoggedIn.value ? (
 					<LoggedIn siteId={ siteId } toggleTray={ handleTrayToggle } logout={ logout! } />
 				) : (
-					<LoggedOut
-						login={ login! }
-						canWeAccessCookies={ canWeAccessCookies() }
-						loginWindow={ loginWindowRef ?? null }
-					/>
+					<LoggedOut login={ login! } loginWindow={ loginWindowRef ?? null } />
 				) }
 			</div>
 			<CommentFooter toggleTray={ handleTrayToggle } />
diff --git a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/state.tsx b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/state.tsx
index 88fa7047f019..c3db6b7a8c8e 100644
--- a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/state.tsx
+++ b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/state.tsx
@@ -10,6 +10,11 @@ import type { Signal } from '@preact/signals';
  * @return An object containing all the signals used in the app.
  */
 export function createSignals() {
+	/*
+	 * Cookie access can't change without a page reload, so probe once and share the answer.
+	 */
+	const canAccessCookies = canWeAccessCookies();
+
 	/*
 	 * In userInfo we store the user data for logged-in users.
 	 */
@@ -22,7 +27,7 @@ export function createSignals() {
 	const userLoggedIn = computed( () => {
 		return (
 			VerbumComments.isJetpackCommentsLoggedIn ||
-			( canWeAccessCookies() &&
+			( canAccessCookies &&
 				userInfo.value &&
 				userInfo.value?.service !== 'guest' &&
 				userInfo.value?.service !== 'jetpack' )
@@ -77,12 +82,22 @@ export function createSignals() {
 		return ! mailLoginData.value.email || ! mailLoginData.value.author;
 	} );
 
+	/*
+	 * Login is required but the login options can't render, so there is no way for this comment to
+	 * be accepted. `mustLogIn` tracks the WordPress.com session, which is absent in the Jetpack
+	 * iframe even for visitors logged in to the site itself, hence the userLoggedIn check.
+	 */
+	const isCommentBlocked = computed( () => {
+		return Boolean( VerbumComments.mustLogIn ) && ! userLoggedIn.value && ! canAccessCookies;
+	} );
+
 	/*
 	 * Calculate if the reply button should be disabled. When we have no user data we check the shouldDisableReply value,
 	 * otherwise we check if the comment is empty or saving.
 	 */
 	const isReplyDisabled = computed( () => {
 		return (
+			isCommentBlocked.value ||
 			( isAuthRequired() &&
 				! userLoggedIn.value &&
 				( isMailFormMissingInput.value || isMailFormInvalid.value ) ) ||
@@ -117,12 +132,14 @@ export function createSignals() {
 	const subscribeModalStatus: Signal< string | undefined > = signal( undefined );
 
 	return {
+		canAccessCookies,
 		userInfo,
 		userLoggedIn,
 		mailLoginData,
 		isTrayOpen,
 		hasOpenedTrayOnce,
 		commentValue,
+		isCommentBlocked,
 		isEmptyComment,
 		isSavingComment,
 		isMailFormInvalid,
diff --git a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/style.scss b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/style.scss
index 7f88cd7861db..4929d022019e 100644
--- a/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/style.scss
+++ b/projects/packages/jetpack-mu-wpcom/src/features/verbum-comments/src/style.scss
@@ -332,6 +332,17 @@
 							padding-bottom: 16px;
 						}
 
+						// Matches the accent-bar treatment of .verbum-message below. Colors are
+						// pinned rather than themed so the notice stays legible in every scheme.
+						.verbum-subscriptions__cookie-notice {
+							margin-block: 0 16px;
+							padding: 8px 12px;
+							border-inline-start: 4px solid #f0b849;
+							background-color: #fef8ee;
+							color: #3c434a;
+							font-size: 14px;
+						}
+
 						.verbum-logins {
 							display: flex;
 							align-items: center;