Your comments

Yes!

As another user migrating from emacs, this is something I miss a lot, particularly when trying to develop plugins.

I chose sublime text over competitors because of its apparent philosophy of simultaneous simplicity and flexibility. Auto-documentation in this style is clearly fits that approach: it helps solves the documentation problem in a straightforward way and it provides various ways for the user to get that information — statically via generated markup or interactively in the editor.

Please consider this, it would be a huge help, especially to plugin developers. And not only would it help to document the editor, it would also encourage plugin developers to document their code better as well.