The only option I see with this software is to 'require a click' from someone in a specific forum - meaning they must thank the OP in order to reply, and that would suck! I'll peek around and even shoot a message to the developer and see if that's possible what you mention.
My 2 cents, shouldn't happen. There are many times I'll thank someone because I agree or it makes me laugh. No comment from me is needed, thus I thank and move on.
Freedom of expression should include the freedom to abstain from speaking.
"The government is a child that has found their parents credit card, and spends knowing that they never have to reconcile the bill with their own money"-Shannon Churchill