I tried to submit it to addons.mozilla.org but they didn’t accept it.
It sort of looks as if they did accept it. If they were hesitant, perhaps it has something to do with the description suggesting that it’s a broken and pointless temporary kludge, as well as calling Firefox “removed”, and the ridiculously irrelevant screenshot.
I didn’t realise it was that easy to build a simple firefox extension like that. Maybe I’ll modify it to disable the whole clipboard api and some other stuff.