I passed a link to your comment to the matrix chatroom, and the person who likely wrote the text you had seen responded:

The issues themselves are represented using the standard AP Note type, but Mastodon doesn’t seem to understand what ForgeFed tickets are iirc. Since Gitea doesn’t have threads, I guess one solution could be to render Mastodon-generated comments as quote replies on Gitea.

There was more discussion on supporting threading after that comment.