Quote this

Often, one sees "content" that employs "quote marks" for "emphasis". Other times, the author is a bit less "crazy-bananas" and uses the quotes only to highlight slightly "odd" terms.

Of course, quote marks should be used for nothing of the sort. Quote marks, single or double, are intended for use:

• when you're quoting something that someone else has said or written
  
• in written dialogue
• to identify words that form a chapter, article, song, radio or tv title: The post "Quote this" on Backstoryesque discusses quotes.
• to explicitly identify a name or term as such within prose: The paper was marked "Fail".
• to explicitly identify jargon or colloquialisms as such: We call this hairdo a "mullet".
  

This last item seems to be the real sticking point. Why quote mullet but not crazy-bananas? How can you tell when to apply quotes?

If you're explicitly presenting a word as a special term -- as if saying "here's a word you should note or remember" -- give it quotes. If you're simply using the word in prose, it takes no quotes. Thus:

• We call this hairdo a "mullet".
• He had a mullet hairdo and blue suede shoes.

In combination, correctly applied quotes might look like this:

"Boo," said the man. He had a mullet hairdo, blue suede shoes, and "Mum" tattooed on his arm.

I'm not sure whether this guy's rockabilly or just from Reservoir; in any case, he's certainly a character. But not a "character".