Right now I'm working on proper comments threading and nesting for non forum comments. Here is a screenshot of the new default thread style which has been checked in to 1.8:
As part of this work I've determined that forums and comments are too tightly intertwined. I've started a CVS branch, BRANCH-forumslib, in which to fix this. Forums code will be separated from commentslib (Done), and forum topics will be turned into first class citizens. This should simplify the code for bot forums and comments and maybe even boost performance a smidge.