Expected behavior as activity commenting and forum discussion are separate. (only a one way tie-in when a new post/reply is made and the content is sent to the activity stream). You can disable activity commenting on forum posts/topics and blogs postings.
I updated
https://wordpress.org/extend/plugins/buddypress-group-forum-extras/
which now includes an activity subplugin -> will pull in activity comments made to a topic post (no reply ability but at least someone can see the conversation from the stream)
Thanks @etivit (rich!)
I’m a bit confused how this is supposed to work. I’ve downloaded the extras plugins and activated the extras + the activity plugin.
How will it pull the comments made on topic post? Will it be on the forum itself? Does it only pull the comments made on the replies of the main topic and not sub replies? Will it only work for future comments and not for the ones already made on the “main topic”
First, I just found a small bug and fixed it in the trunk – you just need to update the file: bp-forum-extras-activity.php
Second, make sure you add the theme edit (detailed on forum extras wp-admin page)
The comments appear directly underneath the post which has the activity. It pulls in all replies for the given post (so threaded). It will work for any backdated activity comments – whatever it can find for the given group_id and post_id (item_id)
http://files.etiviti.com/misc/buddypress/bp-group-forum-topic-post-activity-1.gif
http://files.etiviti.com/misc/buddypress/bp-group-forum-topic-post-activity-2.gif
http://files.etiviti.com/misc/buddypress/bp-group-forum-topic-post-activity-3.gif
http://files.etiviti.com/misc/buddypress/bp-group-forum-topic-post-activity-4.gif
Thanks etivit/rich ! for the pics, totally more clearer than words
Thanks for the screenshot @etivit (rich!) but I can’t get it to work
I have added <?php do_action( ‘bp_forum_extras_after_post_content_li’ ) ?> to groups/single/forum/topic.php but it still doesn’t display as your screenshots.
My mistake. It works! I didn’t see the ajax drop down 
Thanks for your help!
@antonrsaopencirclecoza
16 years ago
When replying to a forum topic, or any forum comments from the activity stream, it doesn’t add the comments to the forum topic. Is this how it is meant to work? So if I was looking at the forums directory, it only shows for example 1 post in the given forum but actually there’s more as most people replied directly to the forum topic from the activity screen. I know that members can browse the specific group for the activity items but then not everything is in one place as it should be.