In my opinion, you try to make a distinction where is none. What is the difference between showing off and helping others in the context of technical questions on blogs/forums? Yes, you help others by providing solutions/advice for dificult problems. And you get satisfaction from the fact that you succeded where others stumbled and you let everybody know it by posting it online. You prove your value to a group of people, which gives you a feeling of inclusion -> important motivator.
In general, there is no such thing as altruism. You always get something out of helping others that keeps you going. Nobody is truly selfless. Altuists are the species which died out long time ago.
Meh, Ayn Rand is wrong, lots of people do things that they'd rather not be doing for the good of their family/friends/society. I'm not sure why so many people adhere to her antisocial musings. Sure some people only do things that only make them feel good. Altruism exists despite all the Randians attempts to morph it into something else so they can feel better about being greedy/self-centered/self-serving like them.
In general, there is no such thing as altruism. You always get something out of helping others that keeps you going. Nobody is truly selfless. Altuists are the species which died out long time ago.