make a statement about how they identify a part of a group
That’s what it is. A shibboleth. They’re broadcasting group affiliation. The fact that it grates on the outgroup is intentional. If it wasn’t costly to adopt it wouldn’t be as honest of a signal.
On a scale from the purest, not lifting a finger anymore than to strike a keyboard, of virtue signaling to putting one's money where their mouth is this shibboleth is about as costly as the tidal zone is dry land.
That’s what it is. A shibboleth. They’re broadcasting group affiliation. The fact that it grates on the outgroup is intentional. If it wasn’t costly to adopt it wouldn’t be as honest of a signal.