Shouldn't this be:
"A real split infinitive, though not desirable in itself, is preferable to either of two things, real ambiguity or patent artificiality."?

No - that wouldn't have been an accurate quote. And while the amendment danensis suggest is OK (apart from having the full stop preceding a question mark at the end, I think Fowler's version has a better rhythm, as well as being perfectly grammatical, as is only to be expected.
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Many would prefer the apostrophe to be bare of the subsequent "s", so that his comment would read "Lynne Truss' book Eats, Shoots and Leaves".

And many wouldn't. I think it'd be quite wrong. I can't imagine that anyone would ever be likely to actually pronounce it that way, particularly with a one syllable name.
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I think the "Eats shoots and leaves" joke most often involves a Giant Panda. But probably not in Australia.