I could have sworn that I read somewhere in the terms of agreement that soliciting spam is grounds for account termination, as is responding to such threads. Please correct me if I am wrong.
Well, there are no specific penalties for anything here - everything is handled on a case-by-case basis. Spammers do tend to get immediately banned, though.
Responding to spam threads has never been something addressed - generally, the posts get reported quite quickly and are deleted in short order.
As a clarification, the people that we've banned have had their first 3 or 4 posts as spam and nothing productive. We have, in the past, deleted a couple of spam posts, moved a couple actual gaming posts, and then e-mailed the users to double check the rules.
But mostly, we delete the thread entirely, so any response disappears, too.