RE: forward-comment and syntax-ppss

[Drew Adams]

> From where I'm standing, the things you use it for (hide
> buffer contents)

No.  Narrowing is not used to "hide buffer contents".  That's not
the point of narrowing, even if it is one effect.  It's used to
make some buffer contents inaccessible to certain (many, typical,
ordinary) operations.  It is not just you who does not see parts
of the buffer; it is also Emacs features that do not perceive
them.

> can be implemented in a much better fashion using overlays
> with invisibility (in fact, one such implementation exists
> already),

No.  It's not about invisibility.  Overlays do not offer
anything that comes close to replacing or simulating the
effect of narrowing.

> which don't introduce the difficulties of changing point-min and
> point-max. 

What difficulties?  What's hard about changing those?

That's the essential design of narrowing - the entire point
of it: change `point-min' and `point-max'.  If you're not
doing that then you are not in any way giving users (and
code) any kind of a replacement for narrowing.  And if you
are doing that then, well, you're narrowing the buffer.

At the base, narrowing is nothing more than binding the
meanings/behavior of `point-min' and `point-max'.

> Thus, without making things harder for many other facilities.

No one has given an example of how narrowing makes things
hard "for many other facilities" - or even for one facility.