I don’t think “female” is offensive.
I thought it was offensive because some (supposedly female) users said it was offensive; but I didn’t understand why my female friends used the term (female).
I found another saying that it wasn’t offensive, and I immediate copied that belief.
LGBTQ+ politics is confusing …
It’s contextual. “Females” is often a slightly nicer way of saying “removed,” but it’s also often just a neutral term. I’d say the top comment from /u/frankaiden02 in that thread gets it right.