Virtue signaling is the worst interpretation you can have of someone attempting to do better. If someone’s trying to make a small impact on the world, shouldn’t you encourage them instead of making fun and claiming they’re just doing it for looks?

If you believe in the moral of it then it's not signaling in the first place. It's only virtue signaling if you do it just to get acceptance or mating or something like that (e.g. I love barbecue but this girl I'm trying to date is vegetarian so I pretend I don't like barbecue to signal that I'm a good match for her).

The usage of the term 'virtue signaling' is almost always a sign that the person saying it isn't being intellectually honest - it's usually just meant to be a putdown.

if a boycott is a virtue signal then your comment is a vice signal