For sure there is more users than instances. So the amount of requests would be grater but at least they wouldn’t happen at the same time.

But if fediverse ever grow to be as big as other social media, then a single post/link can be viewed by thousands of users at the same time causing the same effect.

Does Slashdot have both up- and downvotes? And if both, do you give a reason for upvotes as well?

The only scenario where I see disabling downvotes as a good idea is when upvotes are disabled as well.

So you either:

• have only number of views (no up/down votes) so people don’t chase virtual points
• or there are both of them so that when combined they result in a fair rating.

Upvoting without downvoting doesn’t show if people like it, nor whether it is good or bad. It only shows that it reached a lot of people and is popular. And that can be achieved with views alone.