I noticed the following behaviour when I downgraded a repo package with -U from the local pacman cache (/var/cache/pacman/pkg) and LocalFileSigLevel set to Required.
When downgrading a package it will fail because of the missing signature file. Technically this is right, but as this was a package from the repo (signed with a packager key) shouldn't it work like it works with -S?
And it kinda looks like, after setting LocalFileSigLevel to optional, that the package and the key is checked, but dunno how to check what happens if the key isn't valid.

So I'm wondering if I'm overlooking some aspects which requires this strict behaviour against outdated repo packages, or if the -U behaviour could be adjusted.