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 . . .

First, in your sentence, the word “unnecessarily” is not only unnecessary, but also a poor choice of words. Think about what you are attempting to communicate with that sentence. You are saying “[there is] no reason to . . . suppress a writer’s creativity by prohibiting split infinitives.” Adding the word “unnecessary” here is not necessary at all, for doing so merely creates a tautology: of course you would think the prohibition on split infinitives is “unnecessary” if you believe there is “no reason” to forbid them.

Second, if the word were indeed “necessary to the sentence’s meaning,” it could easily be moved to follow the word “creativity.” And if you think fixing a grammatical error in this fashion makes you sound like a clown, I should probably clarify for you that the “clown standard” is an objective one, not subjective. A true clown, after all, will fail to understand the problem with split infinitives in the first place, so he will be doubly perplexed if he attempts to revise his sentences in such a manner as to avoid revealing his prosaic handicap.