It seems to me that this arrangement emphasizes the Who instead of the Whether (which obviously depends on, but is different than, the What). The alternative contraction (I won’t) would seem to make the sentence sound more like a general disclaimer than a statement suggesting a difference between its speaker and someone else.

However, you appear to suggest, alluding to what I said in the original post, that someone might just miss the word “not.” But in this case, I think the sentence is unlikely to be misread, because the distinctness of the leading contraction bleeds over onto the specifier that follows it.

As an aside, I don’t think the contractions I don’t and I’d not are at all interchangeable, as the first means “I do not” (indicative) while the second means “I would not” (subjunctive).

The example that immediately comes to mind is “I will not.” I have always spoken/written this as “I won’t” but I have noticed that some people write “I’ll not.” I suppose this example also works for “I do not” (I don’t v. I’d not).

How do your rules of emphasis and persuasion come into play in this situation? Surely these “alternate” contractions create tremendous potential for a misreading . . .