What I'd want will never happen.. but I think it will work well.
Each seller has its own "subforum" - inside there, the seller can post new threads/announcements etc. - this will avoid clutter, and people wont need to search, they can simply go to there seller of choice and freely talk about profiles.
Thats my 2cents, avoid the clutter, avoid the use of unwanted threads appearing for those that don't want them, avoid unnecessary bumping of threads to keep them in top of page.
A subforum per each seller, bam.. off you go!.