C2S API: Reply includes automatic mention & manual mention

[mediaformat]

Quick summary

WordPress automatically adds an @mention when replying to someone.
I'm not sure an ActivityPub API client should expect the server to automatically add the mention on a reply.

The second mention does not appear on the wordpress site, but does appear in the activitypub representation, so it is federated as such

Steps to reproduce

Using an ActivityPub API client

1. Post a status
2. Have someone reply
3. Reply to the reply, adding a @mention
4. See double mention via browser.pub or on remote post being replied to.

See:

• https://browser.pub/https://mediaformat.org/?c=2355
• https://mastodon.libre-entreprise.com/@nuages@mediaformat.org/117080612985393797

Site owner impact

Fewer than 20% of the total website/platform users

Severity

Moderate

What other impact(s) does this issue have?

No revenue impact

If a workaround is available, please outline it here.

No response