Greasemonkey was the good one and then something happened with it and it was no longer the best choice. I'm not sure what.

The same repeated with Tampermonkey. It now has telemetry built into it, at one time w/ no privacy policy.

https://www.reddit.com/r/firefox/comments/6hs59w/tampermonke...

The good one now is Violentmonkey. Has been for some time.

Does Mozilla have an allowlist for these? If so I don't like it.

(Iceraven is a fork of Firefox for Android with way more extensions enabled and several other annoyances fixed.)

I just installed it and then added https://greasyfork.org/en/scripts/460206-hn-avatars - it works perfectly!