It is an individual perception, what the Thanks button means. If it is my post being thanked or if I am thanking someone or reading a post someone else has thanked, etc.; the different situations can change my perception of what the Thanks button is "saying". Trying to decide what it means to someone else throws in a whole different level of imaginative thinking :-)

I only have myself to worry about. If I am glad someone said something I may thank them. It may mean I don't have to write a post myself :-) or I may be thanking them for saying what I think or feel too (and thinking and feeling are not the same!) You'll never know what I mean when I push that button unless you ask me, personally. It is possible that I have not thought about it, merely felt about it in passing such that if you asked me I would not have a ready answer?