> What is this term "virtue-signal" supposed to mean?

LMGTFY https://www.google.com/search?q=virtue+signalling https://en.wikipedia.org/wiki/Virtue_signalling

Virtual signaling is a public demonstration of values, but usually with the negative connotation of an ulterior motive to improve social standing and collect praise.

"Wearing your religion on your sleeve" is an older, similar expression.

I don't think this applies here.