I'm not sure how it's relevant to the issue of group selection and altruism; but anyway such inheritance still seems to be relatively rare, as far as I know.

It's interesting that you call it Lamarckian - the epigenetic inheritance system itself would have to evolve in a normal Darwinian way... e.g. if genes get methylated (turned off semi-permanently) and passed down to offspring in this state, one could call that Lamarckian, but the methylation system itself is in need of a Darwinian explanation.