Without wanting to get into a grammar war, I'm not so sure I agree that it "condones" it. Dictionaries reflect the current state of usage, they don't act as arbiters of correctness. The abuse of "literally" as an emphasiser (which usage is now listed in the OED) is a prime example.
I would prefer "his or her" over "their". Perhaps our American cousins might disagree though.
I prefer "their" rather than "his or her", it is less clumsy & there is no point in specifying gender unless it is relevant!
I agree in that I prefer "their" in informal speech; however in a formal document I would find it sloppy. I don't think "his or her" is inherently clumsy; m
aybe I'm just showing my age.
Besides, some people are neither, or their biological gender is ambiguous - so a few people fit into neither the male nor the female category (depending on precise definitions, about 0.5%)!
My understanding is that most intersex (and certainly all trans) people would identify with one or the other, and even those who don't select exclusively identify with a mix of both (and would therefore still be covered by "his or her", no?) although I don't pretend to be an expert.
Perhaps it would be easier to avoid the controversy by actually rewording into the plural, where possible?
So
"any user can make such a change for his session."
becomes
"Users can make such a change for their individual sessions"
