I will thank if somebody posts something I'm interested in, like a morph I've never seen before, or newborn pics of a morph I like, or if I have a problem and somebody posts solutions and actually seems like they care, or if somebody posts something useful, like maybe something to do with helping people out or what not.
I thank when the persons post makes me feel fuzzy inside. I really feel the rep points are not used enough on this site though. There is a lot that takes place on here(good advice and such) that really deserves possitive rep points in staed of a thank you.