It's difficult to figure out what it considers to be toxic, but so far it seems to be cursing. The medium setting also hid a comment which was an opinion, albeit a bit harsh. Luckily you can mark comments as "shouldn't be hidden". I disagree with other reviews on here that are scared of this extension. It's not censoring either, that's just pushing it. It's just a way to silence the noise. Sometimes when I'm researching something I don't want to get dragged into discussions and people yelling at each other. This extension would be perfect for that.
One very important point I'd like to make though is that it should stay in this specific form. Don't quietly hide comments, the dots that replace the comments currently are perfect. As long as it is opt-in and can be tweaked I think this extension is a great idea.
I do feel there's something to be said about being allowed to post toxic comments yourself even though the filter is turned on. It hides your own comment when toxic (I tested it. Obviously deleted my hateful comment after) but I don't know if that's enough.