Maybe I am pedandic, but whenever the little box tells me I have gained XP, I try to figure out where it came from. Part of this is just silly instant gratitification, but I do have a genuine interest in evaluating the feedback I get.
Anyway, as my nodes have grown, it gets harder and harder to remember what each their reputations were, and try to figure out whether I got ++'d, or did I just get real lucky on my last four votes.
What would be nice if the XP notify message also included the source of the XP change. I would be far more interested in knowing that than how many XP I need for the next level.
I cannot imagine I am the first person to think of this, so forgive me if it has been beaten to death already. My quick search turned up no prior art.