"Normally" such an app (avrider) would be set up with routing such that the url became /forum/thread/<id> -- and with a simple 6-digit id, that's much more managable to type/communicate manually than an uuid or something.
All that said, I basically agree -- exposing some "magic" constant/serial number to the user usually doesn't do much to help with the ux. It's actually an interesting problem: what would be the better, more "true" web/REST-like url-scheme for a forum? Perhaps forum/topic/sub-topic/thread-topic ? How limiting would that be wrt. reorganizing the forum threads (and not breaking links) -- this is especially an issue if there's a chance of re-using uri's -- it's annoying to have a link to one discussion morph into a link to another one. I don't think there are any solutions that are significantly better than a (symbolic/numerical) thread/topic id...
edit: Actually I see the sense in the email-id-like urls of the d-mars forum (or usenet-like).
Back to the 90s URLs.