Even though we know comments are not for extended discussion, comments under the question or answer goes on to become a discussion. There have been a several chat rooms which are imported from comments. When such discussions happen, few users are crossing the line and posting unfriendly and rude comments.
When there are many comments under a post (generally around 20 and keep coming), moderators are moving to chat directly without checking the comments if they are unfriendly or rude. I have flagged some comments as rude and a few as unfriendly and no longer needed. This has happened for me multiple times (A couple of them are still present in chat transcript).Such flags will be marked helpful but the comments will be changed to chat messages.
There is not much of a problem when the comments are flagged as "It's No longer needed" but it is a problem the comments are rude and unfriendly. Moving them to chat without deleting causes harmful content to stay for a long time. We don't want such content to stay for long. It creates further hot environment in chat server with flags and more discussions between user and user.
So, moderators should delete unfriendly and rude comments before moving whole conversation to chat rooms.
Related faq :
Not giving examples because they are rude or unfriendly. Som ewere targeting a community or a region.