I am new here.

Welcome!

But what about just disable downvoting? Good comments will be voted up, bad comments will not be voted at all, and will rot in the bottom. Why remove them?

Downvotes serve a number of useful purposes. We do want to maintain a culture of high standards and differentiate between comments that some like and others dislike and comments that aren't disliked by anyone. (If you only have to worry about playing to your supporters, then you are less likely to be charitable and polite.)