Hi there!

A function to mark if a question is unread. this will be good since you wanna have people answering to other answers in comments..

but if you write a comment nobody really sees that you did it, so if you have this read/unread system, then you could mark a thread/question as unread for the user whos post/answer has been commented.

This way, a user will know if one of his answeres/post have been commented, and thereby bee able to act on it :)

I hope you like the idea.

Jacob hansen