Re: Bidirectional editing in Emacs -- main design decisions

[Richard Stallman]

    The reason for this deliberate deviation from the letter of Emacs
    definition of a paragraph are complicated, but the upshot is that from
    the user point of view, it does not make sense to change paragraph
    direction if the paragraph separator does not begin at the beginning
    of a line.

The only case when the paragraph separator does not begin at the
beginning of a line is when the left margin is nonzero.

Why should these paragraphs be different from other paragraphs
with regard to direction of text?

    As another deviation from the definition of a paragraph, text that
    matches `paragraph-separate' is given the same direction as the
    preceding paragraph.  (By contrast, Emacs generally does not consider
    `paragraph-separate' as part of any paragraph.)

I don't think that conflicts at all with the normal definition
of paragraphs.  The separator isn't part of the paragraph,
but its reading direction needs to be determined somehow.