Great changes! A spoiler tag button is really nice, especially since the formatting for it can be a bit clunky. On that note though, I think it'd be nice to have an alternate format for making spoilers that doesn't literally have the word spoiler in it.
It's also awesome to see that official collections are explicitly marked, but the way it's done is rather odd. It's a button that creates an "Are you sure?" prompt on the screen when you click it. It seems like something that's meant for instance owners.
I think something less obtrusive next to the collection's name would be better for marking official collections. I implemented that with a checkmark in my userstyle, and I prefer it to the button. Maybe have the text "official" show when you hover over it to indicate what it means.
ernest