I pressed the button, just to see (I have nowhere near your self control!)... some sort of "thanks" notice at the bottom of the thread. Seems I can remove it too, if I feel less thankful later on.
PS. Hmmmm... not at the bottom. Right below your post instead (well, that makes sense). Maybe these "thanks" points mount up. We'll see!
What button? I see no such button... It's a weather balloon! ...swamp gas?
It's a new thing I explained hidden away in the new design announcement thread. Basically it's just an alternative to post bumping if all you want to say is thanks. You can then search all Thanked Posts and keep track of your own Thanks that people have given you.