This must be the only place on the web where saying thank you gets you pissed on. I'm going back to lurking, can't figure this place out. Please downvote my "karma" to zero & adios.
If everyone said "thank you" to every post, those would swamp any meaningful discussion. Think about it. On this article alone there would be over 100 such comments.
Generally, you can give a +1 by upvoting. If you have something to add to the discussion, you can add a thank you in that comment, but in isolation a "thank you" really adds no value.
You say thank you by voting up the URL or comment. Literally saying "thank you", "I agree", or stuff like "+1" is frowned upon because it doesn't add to the discussion (see http://ycombinator.com/newsguidelines.html).
