Your feed is pretty much posts from friends, groups, things you follow, and ads. If your friends aren't sharing old rotten.com posts and posting dick pics, it's probably pretty good.
That would surprise me greatly. In my online life I've seen stomach-turning troll content everywhere from Duolingo to bitcoin forums. But really, hasn't everyone?
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 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.