It seems to be against several goals of Creole. There is already
a markup similar to this proposal, less verbose, with end tags which
can be recognized easily, standard and very popular: XML. Since
Creole doesn't use single angle brackets, it would be easy to
mix both.

We're soon going to have assigned a meaning to all double
punctuation signs, so Creole won't be much more complicated
than it is now. I'd suggest to reserve {{{$$}}} for LaTeX math, {{{__}}}
for underlined, {{{--}}} for deleted text and {{{++}}}
and {{{%%}}} for future uses (all optional), and we're done.
Both {{{!!}}} and {{{??}}} are too frequent in plain text to be safe.

-- [[YvesPiguet]], 2007-Apr-2