Well, yes there was. I don't remember when I started it, but before I did that, I didn't do it.
The thing is, signatures are not going to last forever at this state (or sometimes it could be disabled by certain users), so thanking the reader isn't going to take effect when I changed the signature. I feel that signatures could be used for other purposes other than something to end posts by. This is not like Gamefaqs or Deviantart where signatures would sometimes be indistinguishable from real text (sigantures are more recognisable here). Also, it's a trick I learned when some users did that before. I wanted to do something like this, so this is what I came up with. I would admit that it gives me something to remember by, so it seems to be doing OK for me.