Reliably trapping end of paragraph / return to vertical mode

[William F Hammond]

Phil --

You write:

> Many thanks for your comments/analysis, David — much
> appreciated. It would seem that you and I have reached the
> same (sad) conclusions, but you remind me that I have
> another obscure query — how (if at all) can I achieve the
> intended effect of :

I have not tried to digest exactly what you are trying to do.

Nonetheless, without full justification, my guess is that if
one were writing software to format a suitable XML document
type (which could be profiled LaTeX in the sense of my 2010
TUG talk) to either regular LaTeX or plainTeX, one would not
have great trouble knowing whether a new paragraph has been
entered.

                              -- Bill