At the same time, I think that offering a compliment as an end in itself sort of falls under what I was talking about in the first bit - it is like rendering a salute. It's an acknowledgment that the receiver holds some value. - if you see an author you really like, you might walk up to them and say something like, "I just wanted to tell you that I loved your last book." A while ago, I saw a Volkswagen Beetle with the license plate "Feature." I thought it was one of the best license plate puns I had ever seen, and if I had managed to find the owner I would have complimented him on it.
Sticking it back into the evolutionary context, though, we always have to ask why these sort of exchanges develop, and why people respond the ways that they do. In complementing Feature-guy, I'd be offering him a salute on his wit, which is something I value. He might appreciate it (because not everyone gets the plate), or he might discount it (because the joke's so obvious), but I believe that it would all fall under that sort of dynamic.