If I click "reply" to an activity item on My Commons related to a forum post, where will my reply be posted -- on the activity stream or on the forum itself (or both)? A bit unclear. Screenshot attached
Activity replies to forum items are currently disabled. See #387. Your screenshot shows an activity item related to a file upload. Replies to this activity item will trigger an email notification to the uploader of the original file; the reply thread will appear in My Commons for users who normally see the item in My Commons; and the reply thread will show up on the group activity stream/home page.
You are not the first person to have this question. This ticket is mostly a duplicate of #3523.
With respect to activity replies to these kinds of items (friendships, new memberships, file uploads), we can either remove the ability to leave replies, or we could try to improve the UX somehow. Maybe "Comment" is clearer?
Forums are a different story, because they natively support their own "replies". For our previous implementation of bbPress, we redirected the Reply link for forum topics/replies to the forum thread itself (#576). We could fairly easily replicate this for My Commons and the new bbPress. A more complex option is to do two-way syncing between forum topics and the corresponding activity threads. This was built into BP 2.0 for blog comments, and is probably something that'd be worthwhile doing for bbPress 2.x. See https://buddypress.trac.wordpress.org/changeset/8190.
