You might wanna have a look at this: https://bugs.archlinux.org/task/36770
Yeah, but there's less packages in core/community than in AUR. Arch Linux Developers and TUs can agree on some UIDs and GUIDs so packages don't conflict. In AUR you can't. ;-) That's why I said "AUR guidelines", not "PKGBUILD guidelines".
-- Kind regards, Damian Nowak StratusHost www.AtlasHost.eu