exports.5: Clean up EXAMPLES and STANDARDS

There was a missing sentence in the description of the second mount
entry in the example. Fix that and some other bits in the EXAMPLES
section.

Also, make the STANDARDS section a bit more readable.

MFC after: 1 week
Sponsored by: Klara Inc.

(cherry picked from commit f9572577cf5f28d8e7592b4f1fb24c54e8e79783)