“Completely” made up is a bit hyperbole. They’re not random, they are usually in some way indicative of the number of upvotes/downvotes a post is getting.

The reality is that any naive upvote system can be gamed. The more popular Lemmy gets, the more lucrative it will be to systematically manipulate which posts/comments are promoted and which get buried. And a naive voting system that just reflects the raw number of up/down votes is trivial to manipulate. It’s harder than a signal in the noise issue, it’s more of a signal in a deliberately crafted manipulated signal issue.

If Lemmy gets more popular, it’s only a matter of time before it’s forced to come up with alternative methods for deriving post sentiment.