"Here again we are saved by our axiom that the user is a good programmer. We assume the user doesn't need operators to be called multiple-value-bind or invoke-restart-interactively to remember what they do."
That seems as clear a disagreement with your assertion as any.
Even if we accept this premise, it applies only to the core language and (de facto) standard libraries (for which we can assume familiarity). As soon as the language is defined in therms of it's implementation it also serves as a coding guideline and this is where the problem lies.
The difference between something like `multiple-value-bind` and `is?` -- especially in the given context -- isn't quite comparable to what Paul's speaking about there, I think. Adding an '?' to `is`, and an '!' to `map` is hardly at all comparable to making the function's name hideously long.