How does Danbooru treat cover scans?

Are they accepted or not or is it a case by case basis?

Example post #591190 and post #591177

There wouldn't be so many cover-related tags and posts if they weren't accepted.

They're obviously treated like all other scans.

But I think many janitors and mods might not approve things like post #591190 simply because the resolution is so low (as compared to the original size of the cover). And this might be relevant, since lowres cover images are far more widely available online than highres ones.

Am I right?

Well, if it's good it's good. I might unconsciously have higher resolution standards if I know something is a scan though, yes.