Extension seems broken, source code isn't available, and results are wildly inconsistent. It's useful if you don't want to get to know people by talking to them, but the notion of crafting a master list of bigots based on anonymous reports is kind of iffy

Must have add-on

really useful add-ons does not work over add-ons that change the aesthetic of a page (youtube enhancer at least)

Extremely useful for knowing when websites are just not worth your time and/or money.

Also works on individual Wikipedia entries.

Slightly less useful for individual social media users, but still catches the big hatemongers. If you think something should be added to the list, you can easily submit it for review.

You may occasionally come across false positives/negatives, but that is rather unavoidable. Does its job regardless.