I think the general view is more nuanced. If there is a LW theory of selflessness/selfishness, Robin Hanson would be able to articulate it far better than I; but here's my shot:

"Selflessness" is an incoherent concept. When you think of being selfless, you think of actions to make other people better off by your own value system. Your own value system may dictate that fulfilling other people's value systems makes them better off, or yours may say that changing others' value systems to "believing in Jesus is good" makes them better off.

The latter concept is actually more coherent than the first, because if one of those other systems includes a very high utility for "everyone else dies," you cannot make everyone better off.

Many LW members place a high value on altruism, but they don't call themselves selfless; they understand that they're fulfilling a value system which places a high utility on, for lack of a better word, universal eudaimonia.