Feature Request: Sticky Comments?

Imagine a source code file with dozens of line of code, so you have to scroll through them. To keep an overview over the file, it would be perfect if I could insert special comments (configurable or not), e.g.

//* That will be a sticky comment

When scrolling, this comment would flow with the code until it reaches the top of the window and then remain there, until another sticky comment comes up. Just like the grey bar in the iOS contacts app where you can see the current first letter of names.

BONUS: Imagine nested sticky comments, e.g.

//* First sticky comment <- one star = level 1
... code ...
//** Second sticky comment <- two stars = level 2
... code ...

... where both sticky comments stick among each other at the top of the window until another comment comes up.

I'd love that feature. Who else? Is there already a feature like that, perhaps in a plugin?