This is a general-purpose list of possible enhancements to Drupal's forum system that could bring it more in line with functionality provided by traditional forum systems such as phpBB. I've already given some of my rationale for this in my other thread, so I'll refer you to that rather than repeating myself here. (Nutshell: I don't expect this code to just magically appear in the next release or three, nor do I expect Drupal to become the all-powerful forum system to end all others or anything. Wouldn't mind if that happened, though ;)
Though this list is long, it is by no means complete or entirely accurate. For example, I haven't touched too much on certain things like the admin interface, as ongoing work is being done on that part of Drupal. Where possible, I've added links relavent to each item on this list, be they feature requests, bug reports, patches or whatever. I've almost certainly left plenty of things out of this list. I'd like to actually get this list posted sometime. :)
Obviously, some of these are going to be enhancements to things other than the forum module itself. Some might be applied to the Drupal core, or the comments system, or an existing module, or as a new module alltogether. I've tried to arrange these features in a loose priority order. I'd be happy to expand on anything I haven't explained clearly.