Rated 5 out of 5 stars

* More than # spelling mistakes: The number of mistakes is customizable, and the extension uses Firefox's built-in spell checker.
* All capital letters
* No capital letters
* Doesn't start with a capital letter
* Excessive punctuation (!!!! ????)
* Excessive capitalization
* Profanity
...So, you won't be seeing any YouTube comments then? :D

This review is for a previous version of the add-on (1.5.1.1-signed.1-signed).