toStorageRow should return scalar values, no UUID object

This was causing compactRow to freak out whenever a link was
added in a comment (particularly painful when replying to a
logged in user, where text is automatically prefixed with a
link to the user you're replying too)

Change-Id: I665c7f96778720e9fa7709dbbb1252d3921eaf9d
(cherry picked from commit 729dda2370fe1bf76aff6603d8231c0bae3bfb25)