Thanking on ppl's post is a good and motivating deed IMHO. For newbies the Karma
thing might sound a bit unfamiliar. I remember that I did not understand the Karma
thing in first.
Anyway, instead of writing KarmaUp/K++ or something like that, I like the way other forums like the mochigames forum is handling this. They have a special THANK YOU button at each posts (next to the QUOTE, MODIFY... buttons). So, if you like the post, you simply click on the THANK YOU button. If you have clicked on the thank you button, that specific post has a footer saying:
Normal post ... bla bla blub
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Thankful people: benny!, Shockwave, ...
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I do not know if that is possible with our forum software, but I really do like this way of saying thank you cos it makes the whole process more transparently. In addition you still have the ThankYou-Score-Count beneath your avatar.