I wanted a username that would be googleproof

Agreed, the reason I chose beehaw, among other things, was that the focus of other instances was growth for growth's sake, while beehaw seemed to be looking to cultivate a more thoughtful, moderate growth, avoiding lowest common denominator problems that Reddit was plagued by by 2014.

So my rule of thumb would be more to ask "do I personally want to talk about this" than "is this popular and getting engagement" before thinking about posting something.