haha don't worry, Android Market has a refund feature, I can return anything within 15 minutes of the purchase
(only once though, if I buy it again now, I'm going to get charged instantly without an option to return it)
It was activated by default, but clicking the "Tapatalk Signature", I could turn it off or define custom messages. Clicking Customize, I suppose you can select certain forums or situations where the signature is not used, didn't check that.
Now, there would be two ways how to make people stop using the signature if Tapatalk was enabled for this forum:
a) the strict way - make using the signature against forum rules = first use would get you a warning, second usage would cause a 2 day ban.
b) the difficult to implement way - Detect these messages within the forum and automatically remove them from the post.