How much not better than average is enough?

This is adapted from a silly conversation I had about a baseball player. It set me wondering how to describe this sort of wordplay linguistically.

HIM: Do we leave Jay in center?
HER: He's pretty good.
HIM: Better than average maybe.
HER: Not much better than average ...
HIM: Better than not much better than average, I think ...
HER: But not so much better than average that he's much better than average ...
HIM: Enough better than average.
HER: Exactly.

Typography in writing, representing prosody in speech, make it easy enough to sort out what's going on here. But how do you explain it in terms of a linguistic which confines itself to what is verbally expressed?

• How does “traditional” grammar analyze and describe these shifts in scope?
• Are these terms and concepts readily understood by, say, high-school students or moderately advanced EFL students?
• Does any “modern” grammar afford better terms and concepts?

I completely understand what you are asking, I am just not entirely sure how one would go about grammatically catagorizing such a conversation. By terms of traditional grammar, it seems to me that it is made up of a series of:

Litotes: understatements in which an affirmative is expressed by the negative of the contrary (as in “not a bad singer” or “not unhappy”, when actually the singer is quite talented or an individual is very happy)

So as each individual continued to respond to the first litote ("Pretty good"), it created a series of compounding litotes that sought to adequately describe the skill level of the baseball player.

In your exemplar, can you really separate the structural component of grammar from semantics and pragmatics? I don't think so. Repartee has grammatical aspects, to be sure, and perhaps one could come up with some regularities and rules that describe the playful banter of the (I assume) spontaneous, unrehearsed dialogue.

From my perspective, however, it seems the element of playfulness, a semantic/pragmatic component, is the guiding principle. The interlocutors are inventing the grammar as they go along, much the same as a child might in overgeneralizing some "rule" s/he perceives is at work (e.g., "I goed to the store with mommy"), minus the humor (from the child's perspective, that is).

Playing with language could take the form of pig Latin, the "poetry" of rap, and various word games involving rhymes, anagrams, feats of memory, imitating Yoda ("Getting stronger you are, Luke"), or doing what "her" and "him" are doing. It's a kind of one-upmanship in which each interlocutor tries to outdo the other by taking the "rule" that the other person introduces and then building on it within a pretty circumscribed vocabulary (viz., good, average, better, not much, and enough). The person who had the last word clearly had the punchline, and it's mildly ironic because what preceded it was quasi-precise approximating.

After reading your exemplar, a picture of a continuum popped into my mind. It is labelled "average" in the middle where the number value of average is five on a scale of one to ten, with number one being way below average, and ten way above average. The punchline's "exactly" is maybe a couple notches to the right of "average," say, six point five.

Years ago my daughter was learning English. It was a hot summer's day, and the air conditioning was running. A few minutes after adjusting the thermostat on the AC, I may have asked her if she was cool enough, and she responded, "Cooler enough." Now there's a "rule" I could have run with in a sort of verbal riff, had she been able to catch on and play with me. Intellectually, we were not on the same level, obviously. By the way, her locution makes really good semantic--if not grammatical--sense. "[I'm] cooler enough" describes "exactly" her level of comfort: not too hot, not too cold, just right. My adjustment made her cooler enough. Any more coolth and she'd have been uncomfortably cold; any less coolth and she's have been uncomfortably warm.

Perhaps you could characterize the grammar of your exemplar as "adjectivality." Change the words to "brilliant" and "superior," and you could have the following:

He: "Should we keep Casey as our clean-up batter?"

She: "Well, he's had a brilliant season thus far, right?"

He: "Well, definitely more than superior, but certainly less than brilliant."

She: "I'd say a little more than more than superior, but a little shy of brilliant."

He: "OK, why don't we settle on a little shy of shy of brilliant, but highly superior."

She: "Exactly."