I disagree, locality data such as ownership, modified date, comments, permissions even, should not be part of the file, it breaks things like repeatable builds, version control and anything where the contents of the file are considered static.

shadow files (._*) and directory clutter (.DS_Store/desktop.ini) are one solution, but they're ugly and frustrating, having separate areas in the filestore (like a resource fork, but designed to be ephemeral) are a much more sane solution.