It isn’t allowed. For reasons that would take either decades of research into the history of the forum, or somehow knowing the individual psychological motivations of the staffers, they won’t just come out and say it’s not allowed, but there will always be a rationale found that disallows any disagreement with maximalist pro-trans positions, and if no existing rule can be invoked, it will just be the usual “this thread is getting out of hand” or “mod note -warning issued” with no elaboration as to what rule was broken.
Sometimes, mods will even bait people into disciplinary action by asking them questions about trans issues that can’t possibly be answered without breaking the rules.