> The documentation for UNIQUIFY, does not state clearly what
> happens if UNIQUIFY is nil and what the perils are.

Well, it doesn't make the names unique, so you could overwrite
a different autosave file, but does that need to be said?

> Where the doc now says "is non-nil" it probably should say
> "is t" instead.

No, all non-nil values (except the ones in secure-hash-algorithms) work
fine.