bug#49558: fill paragraph in texinfo-mode fails with @

[Stefan Monnier]

>> In which sense do our default values not heed this rule?
> The same line could match both paragraph-start and paragraph-separate.

But that rule doesn't say they can't, it just implies that if a line
matches both then it will be treated as a paragraph separator:

    Lines that start a new paragraph and are contained in it must
    match only ‘paragraph-start’, not ‘paragraph-separate’. 


-- Stefan