Reddit

They don't even get the most obvious alts. I used to mod defaults back in the early 2010s on reddit and there were some notorious spammers and trolls, here's a few notable examples.

One guy in particular chalked up at least 100 alts, there was a whole private subreddit create just to keep track of this person. They talked in a very idiosyncratic way and had a few harassment targets, they'd often go to trans subreddits and find someone to send horrible messages to. Typically when they found a target, they'd create a username for them, like if they found a person who picked the trans name "Jennifer" for instance they'd make a user account "NeverJennifer" then start to send suicide messages, then they'd create alts as they got blocked/suspended etc.

There's a spammer on reddit called Oliver Gaspirtz/Oliver Markus Malloy/Introvert Comics who used to run a bunch of subs between 30-40 alt accounts, mostly to sell their own content and books, and market themselves as a sort of online guru/politics understander type. They had a persona to sell redpill stuff, another for pro-cop propaganda, another for agreeable liberal takes. They'd have accounts with bios like "I'm a trans woman!" or "I love Ukraine!" for whatever the hot topic at the moment was they wanted to speak on behalf of. Recently they had all their main accounts and subs deleted apparently after harassing co-moderators of other subs. They still run a smaller network of subs though, mostly for self-promotion.