The warm feeling I get is that it's the syntax I use all day on reddit and GitHub. The syntax could be a mixture of Perl, non-printing characters, Emoji, and a Turing-complete sublanguage, and I'd still use it.
Familiarity trumps all other merits. The easiest language to learn and use is the one I've already learned.
Asciidoc works on github, too: http://asciidoctor.org/news/2013/01/30/asciidoc-returns-to-g...
edit: Thanks Titanous - I assumed it was an optional text filter or something for general use.
Which is key among the reasons I _vastly_ prefer composing longer-form content there than on G+, which has its own bastardized, incomplete, inconsistent, buggy, poorly-parsed tagging format.
Though I do wish that Markdown used the G+ syntax for bold vs. italic:
*This is bold*
_This is italic_
_Markdown italic, ALWAYS_
**Markdown bold, ALWAYS**