i cracked myself up at work today thinking of this extraordinary bit where Hexbear allowed for custom pronoun options and I set mine to Gangster Spongebob
it's completely unpronounceable and also if you clicked someone's pronouns when replying to them it would automatically add the tiny little picture for you
Mostly context - the one joke uses the idea that any identity other than man or woman is pretending to be something you're not, while the "my pronouns are [complete incoherence]" highlights how all genders and pronouns are made up.
As a cis im not really qualified to make a statement of meaning, but since you ask, i think that custom pronouns could be cute/fun/meaningful for enbies or anyone to express their sex in a thousand words rather than 2. However my comment was (perhaps) in agreement with you, saying in essence it would be used too often by trolls or general baddies.
This is literally why we don't have custom pronouns.
We actually had a whole discussion way back; parts of the mod team wanted custom pronouns, parts of it thought it'd end up turning into a jokes field. I still agree with the decision. Though we also talked about having custom user flairs, like back in the old sub, and I thought that custom pronouns would be fine if we added those first, since it gives you a place for your joke and allows mods to be bigger hard-asses about jokes in pronouns.