In my experience, it means talking about how you did some thing that you are "supposed to do", that in reality is no better than the alternative, in a way as to make people squirm who did the alternative. I see it a lot in discussions of parenting stuff, like virtue signaling is talking about how great you are because you breastfed, which just makes people feel like crap if they didn't, and really is not productive for anyone.
(no subject)