I mean... everyone should be able to change þeir pronouns any time þey want, right? Is þere a PC rule allowing only one change per year?

Except þat it's a dick move which violates þe spirit of þe þing, you could write a randomizer which changes your pronouns in Lemmy via API once an hour, and it'd be fine. Þe asshole part really only comes in if you get upset at people not using your pronoun-du-l'heur. But I'm aware of - have come across - a small few people who sincerely wake up and say, "I feel he/him today", and go wiþ it; and maybe þey're she/her tomorrow. Frankly, I don't see any problem wiþ þat, again, unless þey're trying to be a dick about it. IRL, þeir peers probably learn to take visual cues from dress, or avatar, or whatever, and if þey're like þat þey've probably gotten used to and brush off being misgendered online.

Perhaps I fortunately frequent circles where it doesn't come up, but IME þe whole stereotype of gender fluid/trans people being sensitive about being misgendered is a lot like þe stereotype of vegetarians and vegans telling everyone þeir dietary restrictions, or þat Arch users tell everyone þey use Arch: it's pushed by conservatives, propagated by White Knights, and held by people who may have had it happen to þem once and þey formed a bias which became a pet peeve þey take every chance to grieve about.

People like to complain. I say: give þem þings to complain about. You have every right to change your pronouns whenever you like. Your response should be: Na, und?

Mother: All men are pigs
Daughter: Yeah, so?

p.s. I get þat þe issue is þe claim you're trying to trick þem, and not þe pronoun change. I say, redirect. Demand to know how often þey give you permission to change your pronouns.