I got some abuse here for answering every post instead of leaving brief comments in the "thumb": I'd assumed from other fora that is was just a "like button" to accrue "reputation" to the user - a system I've always loathed as a teenaged wankfest.
Don't change it. People are used to having a bunch of one line comments in the "thumb" after posting a pic. And these threads of several hundred pages are bad enough as it is!
Anyway, a suggestion:
Buying and selling is a nuisance with so many posts to plough through. Would it be possible to build in a search by size function and make the buy and sell more of a database with standardised parameters, like eBay does? This isn't just for the convenience of the buyer - although I would like it. It's for the seller, too: if you're selling, say, a pair of shoes, you've got a much better chance of someone searching by their size deciding they like your shoes, than someone who likes shoes being bothered to search through every single thing they like hoping something is their size. Search by size is one of the most effective attributes of an e-commerce site, as it encourages browsing and impulse buying!