Not really, no.

I actually only added that line as a postscript to not sound like I was making some kind of feeble boast. Ie: 'I've seen things you people wouldn't believe: racist memes on Etsy, animal carcasses on glassdoor.com...'

And I actually really wonder if other people see such things, because I really don't. Not saying they don't exist, but they don't seem to get pushed into my "timelines". What you could find if you were looking for it I don't know.

I've seen Goatse, though - maybe it's just that everything else pales in comparison.

Duolingo?

Duolingo had (or perhaps still has?) language forums. Duolingo used 'move fast and break things' moderation, and as a result there was a constant trickle of posts by racists and perverts.