>> It's not so much surface API
>It's a new static method defined on the publicly accessible "surface" of the jQuery constructor function object.
>> It's not so much surface API as it is a simple hook. It's clearly marked as private (leading underscore).
>An underscore is _meaningless_.

We don't have to document this as a prime citizen in the docs. We can just mention it in the custom build part of the docs. This is _not_ public API, it is a _hook_.

And, _yes_, prefixing a method with an underscore is a known and accepted convention in javascript used to note it as private. If it's good enough for jQuery UI widgets, to take an example close to home, then it's good enough for jQuery core.

>> when a private overridable hook on the jQuery object does the job perfectly.
>This is contradictory.

No, it is not. Please read above.

> When did jQuery get in the business of doing insane shit to support phantom third-party Ajax libs?

Since we support building a version of jQuery without the default ajax implementation. Unless you're advocating we remove `manipulation` together with `ajax` because of this tiny bit of dependency.