Probably fix excessive "(authored by X)" attributions

Summary:
This is a pain to test, but we do a lot of needless "X committed thing (authored by X)" right now.

I think that's because we compare two handle links here, and they're never the same, even if they're both links to the same object.

Instead, compare the author and committer more carefully.

Test Plan: Will do it live.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D11635