So much internalized transphobia here.

First of all, stop policing how people look. Nobody is obligated to look a specific way to qualify to womanhood. Such a concept is disgusting and degrading to ALL women.

Secondly, any claim of "We can always tell" is automatically false: The accurate claim would be "We can always tell when it is obvious". You cannot claim to have positively identified trans people to any degree of certainty because I guarantee for a fact you haven't gone and performed a karyotype test or demanded a birth certificate from every person you see.

You assume that if they don't look obvious, they must be cis.

I refer you to the recent Sierra Schmidt debacle: Hordes of gender criticals gathered to declare that Sierra was "performing a terrible idea of femininity" and an "insult to women everywhere".

Sierra of course, is cisgender.

Apparently, you can always tell.