Am I being over-paranoid?
Probably. It depends largely on how you used your passwords in the past.
If you used a different password on every site you visited, you have nothing much to worry about. A bad actor who stole and used your password on one forum would have to do it all over again to get into your account on another forum, which is just too much work -- and the worst they could do is post while pretending to be you.
Where it gets worrisome is when (like a lot of people who use the Internet without thinking) one uses the same password on multiple forums, their work PC, their online banking site, their medical records, whatever. Of course, the hacker will try the same password with that user's other accounts, and bingo! (And lots of people use passwords like "password" or "12345", which just makes the hacker's job that much easier.)