Tumblr may be the site that birthed the 'sending random strangers messages to let them know that they're following someone who's Problematic' social construct, but purity checking comments on Tumblr SPECIFICALLY are so wildly funny to me. I mean, it's a chaotic weirdo nerd site from top to bottom, utterly inscrutable to people who aren't living with at least SOME level of internet brainrot. So you'll be reading a post that's- I don't fucking know, it started as a random aesthetic photo or something, but then the replies on it d/evolved into a funny conversation about sapphic rat psychology. Then someone shows up in the replies, in the middle of everyone having their fun little group improv comedy session, to be like 'just FYI, the 3rd bit part player in this reply chain had a public crash out about the parameters by which the hardness of gemstones on the Mohs scale are determined, during which they used slurs they cannot reclaim, and ALSO they're a proship babyfur.'
You need to have a fluent understanding of at least 5 different weird niche subcultures to be there, to understand what everyone is saying, AND to know that the person leaving that comment is probably just trying to harass and defame a harmless kinky transwoman again. Fucking incredible.