Thanks for the keen observations.
You were right however, let me explain: 'thanks' are an addon to the forum framework. Which means that the core forum software itself isn't really aware of the 'thanks'. The thanks are stored on each post, and in a counter on the user. So when a thank-you is given, the post gets a thank-you with a 'userId' added to that post, so it can link to that person. Next to that, the user that receives the thank you gets his thank-yous incremented by 1.
If the forum core removes a post, it never removes the thank-yous, nor does it reduce the amount of thank-yous.
The same happens when we remove a user from our forum, it removes all of his posts, but all the thank-yous remain.
There is an option for us to re-calculate everyone's amount of thank-yous, by looking at the thank-yous of every post, and iterate through that. We've just never done that, dunno how long that will take.
I'll have a talk with kwuk about it.
Regardless, thanks for the observation, it's nice to know how people feel about the whole forum and if we can improve it.