This being posted in a Lemmy.world forum is especially poignant given that it seems to be by far the instance most riddled with state and political actors trying to manipulate opinions, with quite a number of those being actual instance admins or moderators of large forums there.
Beyond that and more in general, on certain subjects it's pretty obvious that there are people going around using either bots, multiple accounts or working in synchrony with others to "juice" the impact of their posts - you post something well thought and reasoned which is critical of one of such people's posts and when they respond to it with their own post, within a few minutes their post has 5 or 10 upvotes and yours the same downvotes, yet when you come back and check it hours later, unless it's deep down in a tread, everybody since has been upvoting your post with no upvotes for the other one.
In some things there's also this funny effect that might be due to bot/propaganda farms or geographical: for example, as an European with an European point of view, I'll often in Politics forums point out the hypocrisy of some things said and done by US Democrats and the tribalist types over here pretty much parroting the party propaganda line, because for me who have a far broader political culture than if had only experience American Politics, it's painfully obvious, and if I do that during the afternoon and night here (so morning and midday in the US), it quickly attracts a lot of downvotes, yet often if I check it out later, that post is slowly attracting more upvotes than downvotes and ends up with a slightly (or at times strongly) positive net vote, which I believe is either because there are actual organised propaganda activities on major Lemmy Political forums by the US Democrat Party and they focus on going after fresh posts in such forums and move on after a while (so their impact on votes is front-loaded) or people from geographical locations other than the US are far more likely to have a view on US politics similar to mine than Americans (so I'm getting more downvotes during US prime Lemmy-usage time and more upvotes the rest of the time).
Mind you, this is all self assessed "strange" observed patterns, so take it with a pinch and expect it to be heavily tainted with things like Confirmation Bias.
