saying thank you

I don't think earning would be deducted but you won't get earning for it, I think it is only adviced to answer replies with an actual answer not just thank you....

I dont really know, because that doesn't make any sense. Why would you get less money for that. Your making someone feel better letting them know that they really helped you with something. It might be because if more people reply to your discussion and they're basically saying the same thing, it might make them feel bad because you didnt say thank you to them.

I'm not sure if the earnings will be deducted by saying "thank you", but I've read this from the discussion guidelines:
DON'T:
Thank everyone that responds or comments on your discussion. This will not increase your earnings.
I'm thinking it just won't increase your earnings for saying "thank you" in your own discussions. But, if you are being polite and want to appreciate those who responded in your discussions, I guess it should be fine. I always said "thank you" to those who responded to my discussions, but I always add on my comments too, not only two words "thank you".