<< Imagine a highly skilled author who recognizes a younger one that misuses a semicolon or has poor grammar; the older says to the younger >>
I cannot imagine a highly skilled author who never employs split infinitives. Show me that person.
Regarding semicolons, here is Kurt Vonnegut's opinion on them: "Here is a lesson in creative writing. First rule: Do not use semicolons. They are transvestite hermaphrodites representing absolutely nothing. All they do is show you've been to college."
Is that good advice? Perhaps for some writers, it actually is; but it's not about the semicolon, really, but about stilted, bad writing.
<< Isn't this a prescriptivist rule? >>
I was responding to the previous comment "It's also _descriptively_ true that many people regard certain rules as inviolable, which certainly means that prescription is, in some sense, completely reasonable: comply, or we'll refuse to accept you." My direct answer is "It's the prescriptivists 'refusing to accept' who should worry about acceptance, since they are failing on so many levels it's hard to know where to start"