I'm using opera mini to they the site, it works very well, but that is not the crux of my suggestion. (However it might help the above with their login problem)
what i'm suggesting is that mobile devices are detected and sent a low memory version of the forum, as mobile users are often charged per unit of downloaded data. the other site reduced from 9kb per page view to 1kb. a page on retrobike is typically 5kb.