If someone is doing something because they think it makes a real difference, then it's not virtue signaling by definition.

Those are orthogonal. You can either think something helps or it doesn’t and virtue signal in either case.

It’s right in the name. When you “virtue signal”, you are signaling morals to a wider audience. It’s “virtue signaling” regardless of conviction.

I think you didn't read @JohnFen carefully enough.

If the reason I am doing something is that I believe it will create results independent of being seen to have done it, I am not virtue signalling. Which is what @JohnFen said.

Conversely, if the reason I am doing something is because of the signalling value I believe will be attached to the way others see my actions, I am virtue signalling. Which is what you said.

Virtue signalling is typically something easy with no real inconvenience to the person doing it.

So doing a #supportsoupkitchens on a twitter repost vs actually going and volunteering at one.

I think the OP just overestimated how much electricity charging their phone actually uses, and not intentionally trying to claim they're being useful by saving 1 cent of electricity.