Update code throughout linterReporter for better style and performance.

Mostly fixes from previous PRs of mine. Some (seemingly) better comments and ways of doing things.

@MiguelCastillo: I'll add comments on the lines where I want to better document why the change was done. (**Edit**: Finished adding comments).
`line != null` will also resolve to true if the value is an empty string or a 0... I think this is good.