Re: Emacs Lisp manual issues regarding overlays, display properties, margins, etc.

[Richard Stallman]

    Can this please be documented?  Both that no ?priority? property (or a
    value of nil) is equivalent to a value of 0,

Ok, will do.

                                                 and how priority works
    for overlays with the same priority.

I am not sure which overlay wins when they have the same priority
and same span.  I think it is better not to depend on that.