It seems like this syntax tries to solve a problem that AsciiDoc or Atlassian’s Confluence Wiki Markup already addresses.
Just for the record, Babelmark 3 shows that MD4C, which is aiming for Commonmark compliance, currently supports the no-number style:
. foo
) foo
but not with paired parentheses:
() foo
( ) foo
Pandoc, on the other hand, supports the number-sign style (when not running in strict mode):
#. foo
#) bar
(#) baz