Hello,
Okay, to reproduce this:
1. Create a new group discussion in group
2. Go to the dashboard and comment discussion
3. Open group where you created the discussion and there you wont see any comments, when you press on "Comment" it shows 0 of 1
Commented from dashboard
This showing up In Group view
Added comment from group view
In dashboard
Also, if this is a discussion you should discuss only in one place not adding comments + discussions, found some topics you plan to merge comments to discussions.
Also some time before was the same with commenting on forums topics, support just removed comment button from forum items