A gaydar doesn't have to depend on how gay a person looks superficially. There are plenty of other cues.
True, I should have used more general wording than "looks gay;" it would only be one component of the gaydar criteria. The problem is finding how to state it in not-loaded language. It would be impractical to use "matches stereotypically effeminate behavior."
This is a thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. The previous thread is at close to 500 comments.