I've noticed a couple of things:
1) unless I've missed something, none of the ads show any date;
2) unless you know better, you would assume that the listings on the Buy and Sell page here: buy-and-sell page are complete. Unless you click on one of the headings (e.g. "Darkroom") you won't learn that there are more, older listings. A link on the bottom of each section such as Older Darkroom Listings would help;
3) does posting a query automatically send a pm or email to the person who posted the ad originally? It is not clear whether we need to send a pm or email to him/her. If so, a direct "contact" link would be useful - EDIT - I've just found the "Make Contact" link under the small "Options" tab - it wasn't easy!;
4) are there any rules posted on how the search function works? I tried to search for Mark Fisher's ad for LED safelight bulbs. "LED" yielded nothing, "LED bulbs" yielded nothing useful, and only "safelight" helped.
Hope this helps.