In the 1950's, the British philosopher J.L. Austin came to Columbia to present a paper about the close analysis of language. He'd just explained that, although two negatives make a positive, nowhere is it the case that two positives make a negative, when from the audience a familiar nasal voice muttered a dismissive, "Yeah, yeah."
Thanks for your comment on prescriptivism, Dan. As for this reduplication issue, I've considered this idea with friends after a phonology class we once had. English doesn't seem too keen on them, but there is one that we, at least, believed to be an example of reduplication:
"Do you like him, or do you like-like him?"
As I'm sure you know, many African languages use reduplication even as a derivational morpheme, so it's extreme in their use, unlike in ours.
In the South, where "Coke" can mean any type of soda, I often had to order a "Coke-Coke" to make it clear that what I wanted was a Coca-Cola in particular.
P.S.: I was in college before I realized "I Saw Mommy Kissing Santa Claus" wasn't about an affair. Really.
Maybe one person makes nice, and two people together make nice-nice.
Sounds a bit childish to me (but then so does 'makes nice').
An episode of "Curb Your Enthusiasm" offers this advice: You have to make the nice.
Thought you might enjoy this piece on reduplication: