TODO removal

For each of these TODOs:

- If there's an active bug tracking the work, and the TODO provides
  something of value, I left it and standardized the formatting. I also
  added comments to the bug.

- If the comment provided no value (implement feature X when we do feature
  X), I deleted it with impunity.

- If the comment was stale (won't fix or just out of date), then we
  removed it uncerimoniously.

There was a single TODO that was actually actionable, so I enabled that
test.
`Assert.Null`