Wrong variable

Applies to https://github.com/GigaOM/gigaom/issues/5398

Wrong variable. `$comment` is undefined here.

Switch to `$feedback` as in the other email notification function:
![screen shot 2014-09-26 at 12 02 08 pm](https://cloud.githubusercontent.com/assets/929375/4423630/7c48356c-4596-11e4-81da-7d308a49df1a.png)