Maybe something fancy like, but less ugly colours than, the French style: http://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Le_Bistro
Another option is the standard way of having boxes like in forums and such.
Also, we could have each thread boxed, and then at the bottom of the box, a label 'Replies: ', which would nest the replies.
Version: unspecified
Severity: enhancement