I read that whole thread, in it's entirety, just a few weeks ago.
It's a thorny question and really one of perspective. Caveats about 'lab vs. reality' aside, I think that true altruism comes from attempting good acts without ever knowing whether or not you were successful, or trying to know; merely the act itself is worth it.
I'm not sure how one can accomplish the separation of the act from the actor. For instance, handing over a $5 bill to a beggar might, from the perspective of a casual observer, be indistinguishable from handing over a $5 bill to an armed robber, but I doubt that many people would consider the latter to be the same act
as the former. Yet the only thing that really distinguishes the two actions (apart from the identities of the recipients) is the intent of the person handing out the cash.
I'm not sure I would say that someone who gave money to a robber would be acting under the same intent as someone who did to a beggar. It's the intention of the act that matters, not the act itself.
I don't really consider it valid to say that the feeling of self-gratification that arises from the decision to attempt good acts denies altruism; maybe only under the most stringent definitions of it.
Suppose a person says: "I feel really depressed. I know what will cheer me up! I'll give $5 to a beggar!" She then gives $5 to a beggar, and she indeed feels much better as a result. Was she acting altruistically?
Well, no; the words 'I know what will cheer me up' kinda give that one away.
Instead, let us say that you leave food sitting outside your door, b/c you know that there are starving families living in your neighborhood that you see on your street from time to time. You don't know if they are taking it or not, and you don't make an effort to know; you are simply putting it out there in case someone needs it. That's altruism to me, an act or situation in which you don't know if you are making a difference or not, but acting for the sake of committing good acts. Some would argue that the feeling you get from this negates altruism, but I dunno. It somehow would lack the certainty that comes from knowing
you are helping someone.
I'm also surprised that nobody has brought up the classic: jumping on a grenade. Difficult to argue that sacrificing one's life leads to enjoyment that you 'did the right thing' afterward. Things start devolving into variations of what you would
have wanted and is that some sort of pre-emptive enjoyment on your part...