What should `paragraph-separate' be when adjacent paragraphs aren't separated?

[Alan Mackenzie]

Hi, Emacs.

Suppose adjacent paragraphs aren't separated, i.e. the next one
immediately follows the previous one, e.g.:

   This is the
previous paragraph.
   This is the
next paragraph.

What should `paragraph-separate' be in such a case?  Clearly it should
be null, in some way.  It is not specified at all in its doc string, and
it is unclear in the extreme.

Possible values include nil, "", "\\<\\>".

Should I submit a bug report for this?

As an aside, paragraphs.el is sorely lacking in decent primitives.

-- 
Alan Mackenzie (Nuremberg, Germany).