R1:d7212d855e10

Fix edits of Ponder comments which mention other objects

Summary: Fixes T9806. See some discussion there.

Test Plan:
- Edited a comment with `T12` in it.
- Before change: exception.
- After change: no exception.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9806

Differential Revision: https://secure.phabricator.com/D14539