I've seen this thanks button on lots of other forums. It's a simple form of recognition. Under your user name on your posts it should say 'has been thanked x times in x posts.'
I can tell you it appears it was not a mistake, so all is according to plan. :) I'm sure we'll hear more about it soon. I do believe there are some bugs to iron out (we don't exactly have a a prop...
I realize that the dash is experimenting with different like/dis-like text, so I will save most of my comments for when it is done. Just a thought though, too much clutter under the avatar is dist...
I like the thanks idea it just needs to be cleaned up some to avoid clutter mainly at the bottom of the post telling you all the people that thanked it. A number of people would be fine and simple...