You can't both say "well we let you do it, we're so customizable" and "but if you do and anything goes wrong, it's your fault."

I'd rather that userchrome get removed and Firefox own up to the fact that they're not gonna properly support what users want.

A company who puts users first should not be ashamed of supporting their users' desires. You either support your users or you fight your users. Mozilla have somehow decided to publicly fight their users and furtively and abortively support them in secret; I really don't get how they think that reflects well on them. It feels like Moz are more trying to appease their own UX designers than their userbase.