[JoshTriplett]

That sure is a different thing that some people might prefer. It it not what this project prefers, and that's fine.

To give another example of what is impossible to perfectly detect but still reasonable to prohibit: most projects have a (written or unwritten) requirement of "don't copy code from other projects without respecting their license". There's no reliable way to perfectly detect that someone copied a pile of code from one of their company's proprietary projects, or from some Open Source project under a different license or without attribution. But it's still reasonable for projects to prohibit such "contributions".