Font styles for code review comments

[scotthallock]

Current behavior

Comments that include a carriage return will render with sans-serif font:

Comments that do not include a carriage return will render with monospace font:

Reproduce this behavior by posting a multi-line comment and a single-line comment.

Expected behavior

Comments should render with sans-serif font, except for text that is wrapped in backticks. This allows comments and inline code to be easily distinguishable, and follows standard markdown style.