Well, are you looking for a framework, or something more like an already created package for comments?
As far as frameworks (i.e. literal frameworks) Zend is a good one. There's also CakePHP.
If you're looking for something already put together that is close to what you're doing, I don't really know of any. Although it would seem that forum software would work well. I say this for a few reasons:
1.) Each topic would relate to a specific area or page
2.) Comments are logged and others can see them so fewer "duplicate" issues
3.) Designers / coders can actually interact with commenter(s) for clarification and such
4.) It does mostly what you want already
Or you could use a type of support ticket software like PHPSupportTickets or One or Zero. Then each "issue" could be a ticket, and the manager could assign each ticket a category and even each worker.
There's also Trac (which is a perl script). This is used for bug tracking, but it works essentially the same. Bugs are tracked and assigned categories & personnel to work on them. So you could adapt this to your needs.
All of these are just bases that you could work off of. They each need tweaking of their own to fix things just how you want them.
Hope this helps.
