Inocent Bystander wrote:People like Fowler and Partridge laboriously explain that there is a subtle difference between the two statements ["My advice is not to let..." and "My advice is to not let..."].
Bracketed addendum mine.
I'll use 'em both in meaning the same thing, by which I mean the second of the two. But if I were to be rigorous with my own usages in accordance with how the word order ultimately makes sense to
me, the first one would only mean something in the following sense: "My advice is not to let the boys in: rather, my advice is (that we have a drink, to howl at the moon, that you go shopping, to tell the boys to go hang themselves, etc.)." That is, clarification of advice itself is the focus, rather than merely stating the content of the advice. But to be honest, if I were to intend the former I'd follow with such a clarification, as above, rather than just let the first clause hang. That's just being an enigmatic ass.
Otherwise (colloquially, anyway) for me "...advice is not to let..." all on its own can and often does stand to mean the same as "...advice is to not let...". If a grammar maven should pounce on me for it I can always smile and say, "Ah, yes. What a boor I am. More tea?"
Is that difference the subtley Fowler and Partridge had in mind? It just wasn't seeming all that subtle to me, FWIW. But maybe I'm just tewwibwy wefined, a dewwicate hothouse fwower.
"If you take music out of this world, you will have nothing but a ball of fire." - Balochi musician