commenting overhaul+needs

We'd like to preserve (possibly in one unified technology?) the highly valuable parts of our current system, including and especially the ease of moving comments into the core card content, while addressing the following needs

• signature on first comment
• getting rid of warty "comment" permission (breaks CRUD pattern)
• sorting comments in reverse order
• comment metadata (eg number of comments,  commenters, etc)
• wagneerable signatures (including with images)
• comment short views
• threaded comments?