good ways of signalling "nerdiness"

I would specify instead: signalling "I care about good communication and avoiding misunderstandings due to poor use of language and syntactical ambiguities/misinterpretations"

I've got this idea from I-don't-know-where that this kind of signaling is a useful, cost-efficient sonar ping that'll publicly filter for certain types of people, notably those who care about grammar and those who care about avoiding ambiguities. I think attracting both of those groups is a suitable compromise when the only obvious alternatives are much costlier.