Here's a copy of the AutoMod message just in case the mods cowardly remove it:
Absolutely disgusting. Whoever in the mod team wrote this obviously hasn't used Pale Moon at all and relied on unfounded rumours. I wouldn't be surprised if it turns out to be u/nextbern who wrote this; that guy's a Mozilla fanatic. I wonder if he's getting paid though, all the moderation in r/firefox and preaching about how Mozilla is the best and the messiah of the web must be tiring./u/[username], please do not use Pale Moon. Pale Moon is a fork of Firefox 52, which is now over 4 years old. It lacks support for many modern web features like Shadow DOM/Custom Elements, which have been in use on major websites for at least three years. They also don't have support for many modern JavaScript features, TLS 1.3, WebP images, and AV1 video. Pale Moon uses a lot of code that Mozilla has not tested in years. They have no QA team, don't use fuzzing to look for defects in how they read data, have never published a CVE (mature software teams report their security bugs), and have no adversarial security testing program (like a bug bounty). In short, it is an insecure browser that doesn't support the modern web.
What's weird is that they singled out Pale Moon, and don't attack Waterfox Classic which has some problems we also have and is arguably more insecure (look at all the security advisories they haven't addressed yet!).