I use Firefox with uBlock (standard lists) and uMatrix (all Twitter-related requests permitted) and it's still buggy as hell.
If I try to paste anything into the "compose tweet" dialog it just completely crashes with a very helpful "something went wrong" message.
If I try to cut and re-arrange parts of my tweet, it duplicates all the text and puts it out of order.
The tweet box is not even a <textarea>, it's a <div> stuffed full of <span> elements.
Additionally, the tweet box <div> is nested over 40 layers deep in a massive pile of divs.
As always, they're trying to be way too clever for their own good.
I'm not at all surprised they need polyfills for that trash.