No Pun Intended

While reading a post on Vinography, I was struck by this sentence fragment: "it's actually a great distillation (no pun intended) of the issues."

We could debate the merits of "distillation" as a pun here—though it's an important part of the reverse osmosis process that reduces alcohol levels in wine. But my eye stuck on "(no pun intended)." (And I should note that this isn't a snipe at my friend Alder, but his post is the one that triggered this thought process.)

This "no pun intended" is a common practice in American prose, at least. I imagine witty British writers intend their puns with aplomb. What prompts this phrase? Is it because we hold puns in such low esteem that the author who makes one needs to separate himself/herself from the joke? I'm always happy when I can insert some subtle pun into a piece of text, as long as it doesn't sound forced. It adds some color as a wink between the reader and myself, assuming the reader gets it. Probably most of my puns amuse only myself.

But if the "no pun intended" construct is meant to separate the writer from a moment of linguistic happenstance, it also makes the reader more aware of the pun by interrupting the flow and calling attention to the offending word or words.

Thus the biggest paradox of "no pun intended." It means the exact opposite. Perhaps the punning word originally came to the author unbeckoned, but the writer has obviously noticed the pun, and then s/he chose to leave it in the text, pushing it into intent. Alder could've used any number of synonyms or alternate constructs—"snapshot" has fewer syllables and more Anglo-Saxon roots while "condense" lives one conceptual hop away from "distillation" and offers a more active verb—but he chose to leave the pun in the text, probably because at some level it tickled him.

So we are amused by puns, but we can't be seen to admit it. Or is there something else going on?