The term has been diluted I guess, or this is a strawman. I've never seen real life protests or action called "virtue signaling" before. That's absurd.
Back when I first started seeing the term used online, somewhere around 2009-2013, it was being used to describe the non-religious version of people making "hopes and prayers" comments online.
Like people using filters over their Facebook profile image to raise awareness of something and then patting themselves on the back for a job well done. That problem sure was solved!
You think something the Russian invasion of Ukraine is bad? And you feel that so strong you're going to make a post online about it? You sure showed Putin with that one!
At least taken in the most forgiving light, it was sneering at the type of people who were explicitly preformative with their sense of justice. The type of people to do the day of silence about LGBT bullying, who would then strut around afterwards as if to say "We did it gang! We solved LGBT hate!" Then continue to use LGBT terms in derogatory ways and bully LGBT people.
I always thought the phrase was pretty self explanatory. It's virtue signalling, not seeking, not spreading, not defending, not living, not actually embodying.
This wouldn't be the first time this comic creator made a strip against something that seems to be a ridiculous strawman to me though.