The Help tab is of course under-used, and nobody notices it.
By creating a means by which it can become more relevant in specific situations, you make it attractive to call it out more.
I suggest a cool, just-attention-grabbing-enough feature, to call out the Help tab. For example, a little hovering arrow that says "Special help here". I am "a front-end developer", so I might be able to help you with this (jQuery/CSS) subtlety.
Allow a note to show up as an admin notice on a New post/page/etc., but still always remain in the Help tab
This would allow a user to be "bugged" just enough about information in their face, but still reminded that they could always go and find it when they wanted.
Again, if I am suggesting it, I should make at least some attempt to help make it happen, if you want. (I mean, cuz I can).
Enable hiding of Site Notes top-level admin menu from Settings > Site Notes
This would be very nice, because it would hide it but it would still not be hard to get to.