At least here in the United States, those are usually sold by charities that benefit various veteran's organizations, so there's some actual skin in the game there.

Good question. I think it would on the motivation of the wearer.

If if they are wearing it primarily as a method of socially fitting in and signaling to those around them then it might be "virtue signaling".

If they would continue to wear a poppy on remembrance day in contexts where the people around them did not know what it meant then there's clearly something more than signaling going on. Perhaps it is their tradition, or it helps them remember.

(I should caveat that I don't think there's anything particularly wrong with social signaling so I don't use the term "virtue signaling" as it seems to have a pejorative or sarcastic connotation.)

Remembering?

"Western imperialism"? How exactly was fighting against Germany in WW2 "Western imperialism"?