My place of work heavily uses the forum for keep track
of what's going on.  Some of the the things we noticed
would be helpful are 2 of the following features:

A moderator (or owner of a message can do the same),
edit message, remove from forum category, or move
message to different category.

Sub categories.  For instance, there can be a hierarchy. 
An example could be like one about music.
  Music -> Country | Rock | Rap -> Forum

Thanks a bunch!