I'm confused why people think virtue signalling is a bad thing in the first place. "Hey, you're doing this very good thing just to show off how good you are!". Oh no, how terrible.
Virtue signalling is a term to describe people that are doing harm to a cause or providing no benefit to it, while also aiming to maximize the admiration they receive from others.
That is at least how it's meant to be used. tptacek isn't wrong to point out that the Right generally uses it to denigrate people that are trying to do good just because there is a little 'show' with their 'action'. This is evil because people shouldn't be dissuaded from doing good things. In fact they should be celebrated. The Right have pretty much completely missed the point of talking about signalling, which is credible/costly vs. cheap.
What I think you're missing is the subtextual meaning of "virtue signaling", which is, essentially, "there is no virtue except virtue I condone".
Since that's obviously not the case, most --- maybe pretty much all, in fact --- of the time the term gets used, it's a nihilistic attempt to shut down the good works and careful thoughts of others, casually calling into question their good faith, solely because their broader intentions don't square with yours.
And, as I said, those are the kinds of people we laugh at when John Goodman hucks a bowling ball into their gut. I'm laughing a little bit right now just thinking about it. Again I caution though, it could be more about Flea.
The textual meaning is in my opinion more important, and more often than not completely lost on people. The term 'signalling' is a bit of biology/economics terminology and people aren't very familiar with it. The idea of cost-based credibility isn't expressed within the term, but must be learned beforehand. So they just say 'virtue signalling' because it sounds clever and it remains opaque to them...