I recommend Okular

Edward Snowden remarked:

Arguing that you don’t care about the right to privacy because you have nothing to hide is no different than saying you don’t care about free speech because you have nothing to say.

There is a wikipedia article regarding this argument

I agree, someone has to store and maintain your data, but giving all instances access to it is a risk that could be avoided

So you can get the users voting on posts on other instances?

Could it be anonymized, so you can get exact up/downvote data from your instance, but when it comes to other instances you only get the absolute up/downvotes?

So any instance admin can analyze all users upvotes/downvotes and possibly derive political standpoints, likes/dislikes, opinions and location data from it