I think the dubious assumptions in the two versions of the Mona Lisa one are equivalent; what's implied by "being overrated" is the same as what's implied by "r

I think the dubious assumptions in the two versions of the Mona Lisa one are equivalent; what's implied by "being overrated" is the same as what's implied by "really deserves". If you think "false impression" is bad because "the impression is false" has a copula in it, then congratulations: you just abolished adjectives. "... the red bicycle ..." -> "the bicycle is red". Whatever the problem is here, it isn't is-ness. I completely agree that rewriting what you say in a restricted subset of English (or whatever natural language) has value for seeing what assumptions are slipping in unobserved. It's totally not clear to me that "is"-less English is any better for this purpose than, say, adverb-less English or e-less English; I suspect that most of the gain comes from forcing yourself to write with a strong constraint, which makes you think more. It's not so very different from (one reason) why poetic and musical forms (sonnets, sonata form, haiku, fugue, ...) work well. I wouldn't be surprised if forbidding "is" were a bit better than those, for various reasons. But I suspect that the bulk of the winnage comes from the mere fact of being constrained.