I had my Reddit very heavily curated, my subs were mostly smaller subreddits. I was incredibly active and had my settings so that anything I voted on would not appear on my homepage. I got to see a ton of posts because of that.
Around 2021, I started noticing that reposts weren't just people coming in and posting things we've seen a dozen times because they had no way to know it was a repost. It was bot networks that would take top posts and then other bot accounts would recreate the original post's comment section. The accounts followed patterns and became really obvious to spot after a while.
The original tells were the bots taking really specific posts that only made sense in that context. Popular post from last Christmas? The bot doesn't know what Christmas is, sees a popular post from a few months ago and reposts someone happy about their gifts in August. Look at this beautiful picture I took of the summer Alaskan wilderness this morning but it's February. The photography subreddits were obvious because the bots would rotate the picture a few degrees which would sometimes ruin the picture's aesthetic.
I'm not sure if it was just me spotting them easier or if they were really ramping up into 2022 but by the time they killed API access and I stopped using it, I think over 80% of posts were bots. Made leaving the site way easier.
Fedora Core 4...? I have yet to fully take the plunge but we'll get there.