the biggest issue with reddit/digg/hackernews style comments is how top comments can be gamed for profit. old forums had the problem of "first" and "bump" comments, but steering the conversation was harder.
> top comments can be gamed for profit
That said discord kinda does it and I just can't stand it. Unusable to me.
"Best" is a time-weighted blend of scoring, so that well-voted but late contributions are more likely to be visible despite fewer overall votes. Certainly not perfect, but helps bias away from "first to comment wins"