my least favorite continues to be Reddit, for being a bunch of little hellpits that all seem to attract and maintain the worst moderation staff possible. 

it is legitimately amazing how AITA, legaladvice, antiwork etc. all managed to become great content generators for offsite discussion, and more or less just shitposts and dead air internally, because the minute you e.g. take issue with something discriminatory or tell someone to hire or lawyer you get banned for indecorous posting