First of all, you didn’t answer the questions.

But I will answer yours:

Why do people fear downvotes so much?

This is irrelevant and already addressed in Lemmy. Lemmy already has a disable downvotes config option. Beehaw is an example of where that is used. Anyone who outright opposes¹ downvotes can use beehaw.

Silent downvotes are a different matter entirely. There is good reason to oppose silent downvotes. They are a suppressive act that lacks justification, heavily manipulated, and adds negative value and toxicity.

Re: toxicity -- silent downvotes are also an assault on dignity as they regard the OP as unworthy of explanation. Then there is the further side-effect of the OP being denied the viewpoint of a (cowardly) opposition and ultimately being denied understanding of the community they are in, which is not conducive to future positive content.

It’s ultimately shitty communication. Like when a bank’s way of communicating to you that your ID card expired on file is to freeze your account. Or when in Office Space they communicate to Marvin he is fired by fixing a payroll glitch. It’s that kind of communication that’s shitty. Bizarre how people actually think this is a sensible way to communicate in a civilised society.

If you don’t like the downvotes, you can use a sorting algorithm that ignores them.

There is no sorting algo that disregards silent downvotes while counting reasoned downvotes.

Also, the power of defaults is a thing. The suppression has effect because of default algos used by the unmeticulous masses. One’s own custom sorting algo could not make a dent in that even if it were magically feasible from the user’s view to associate upvotes to downvotes.

¹ I don’t outright oppose downvotes, but when our blunt options are the default shit-show we have by default or no downvotes, no downvotes is better which is why I use beehaw.