Funny, I think HN is the ideal place for this conversation, though it's a bit weird to get there on this thread. But it's a subject of fascination for me personally, and it's a shame that it's taken on weird political dimensions.
I was under the impression that Caster Semenya tends to confound simple categorization like you suggest.
> Sex assignment is the discernment of an infant's sex, usually at birth.
The question is not whether you can briefly look between someone's legs and determine their sex. We know (per the article) that this can fail as much as 0.05% of the time.
The question was what is Caster Semenya's biological sex: the answer is male. This is, in fact, clear.
I was under the impression that Caster Semenya tends to confound simple categorization like you suggest.