Show warning when user cannot federate replies to fediverse comments

[pfefferle]

Fixes #2816

Proposed changes:

• Show a warning message instead of the reply link when a logged-in user without ActivityPub capability tries to reply to a fediverse comment.
• Unify are_comments_allowed() and should_be_federated() to both use user_can( $user_id, 'activitypub' ) instead of the inconsistent publish_posts check.

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

• Create a comment from the fediverse (e.g., reply to a post from Mastodon)
• Log in as a user WITHOUT activitypub capability (e.g., subscriber role)
• View the fediverse comment - should see warning "Your account is not able to reply to fediverse comments."
• Log in as a user WITH activitypub capability (e.g., editor role)
• View the same fediverse comment - should see normal reply link
• Log out and view the comment - should see remote reply block

Changelog entry

• Automatically create a changelog entry from the details below.

Changelog Entry Details

Significance

• Patch

Type

• Added - for new features

Message

Show warning instead of reply link when logged-in user cannot federate replies to fediverse comments.

[Copilot]

Pull request overview

This PR improves the user experience by showing a clear warning message when logged-in users without ActivityPub capability attempt to reply to fediverse comments, preventing confusion where replies would silently fail to federate.

Changes:

• Added warning message for logged-in users without ActivityPub capability when viewing fediverse comments
• Updated documentation to clarify the three handling cases for fediverse comment replies
• Added comprehensive test coverage for local comments, fediverse comments with capable users, fediverse comments with non-capable users, and non-logged-in users

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
includes/class-comment.php	Implements the warning message logic for logged-in users without federation capability, with proper escaping and an extensibility filter
tests/phpunit/tests/includes/class-test-comment.php	Adds four comprehensive test cases covering all scenarios: local comments, capable users, non-capable users, and non-logged-in users
.github/changelog/2816-from-description	Documents the change as a patch-level addition

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[pfefferle]

@davemart-in @robertbpugh @jeherve I would love to have your feedback on the message. See screenshot? Can you think of a shorter one? Is it fine like it is?

[davemart-in]

Thoughts on something like:

This reply won’t be sent to the fediverse.
Enable ActivityPub for your account to reply to fediverse comments.

[pfefferle]

Yes! (Sorry for the missing context)

[jeherve]

This reply won’t be sent to the fediverse.
Enable ActivityPub for your account to reply to fediverse comments.

Should we add a mention that the author will consequently not receive a notification of your reply? Since we have $comment available we could even make that message a bit more dynamic. Something like:

Your reply won’t be sent to the fediverse ; $comment_author will not be notified of your reply.
Enable ActivityPub for your account to reply to fediverse comments.

[pfefferle]

@jeherve Ah, I misread the comment of @davemart-in ! The message replaces the link completely, so it is not even possible to send a reply!

I think it makes no sense to have local replies to comments from the fediverse because this would confuse people even more.