/r/all was also algorithmically curated. Not to mention easily and heavily gamed by bots, trolls, and state-sponsored disinformation campaigns.
That's how we got Trump in the first place. /r/the_donald was constantly shoved in everyone's face, and even Reddit had to eventually admit the system was compromised. IIRC they adjusted the algorithm in an attempt to counterbalance it sometime around...2017? I forget exactly but it was definitely too late.
Lemmy's not structurally better in that regard, unfortunately. If we're not already inundated with bots and other malefactors (big if tbh), it's just because we're not big enough to attract them yet.
Sort of. But the sorting algorithm is not so simple that you can call it neutral or natural.
I don't think the details of Reddit's ranking algorithm are public. Even within a single sub, it's not as simple as counting user votes. That's weighed against age, and all sorts of fuzzy bot/fraud detection mechanisms. I think Reddit intentionally injects noise into the system. You'll see phantom votes all the time to keep things "balanced".
And then in /all, I believe some subreddits are banned entirely, and again it's not as simple as "most votes" or "most votes weighed against age".
Here's a Chicago Tribune article from 2016 that mentions the change I mentioned before: https://www.chicagotribune.com/2016/12/01/reddit-to-crack-down-on-most-toxic-users-of-pro-trump-forum/
It's light on details and again, I don't think details were ever published. Reddit is closed-source so really it's anybody's guess how they're really ranking posts.