I assume the spec is descriptive, and fenced code blocks are 1. a pretty common extension and 2. generally added the same way everywhere

Reddit and GFM use the same table syntax. Reddit is huge [1]. GFM is widespread.

PHP Markdown, MultiMarkdown, etc also support that syntax. Stack Overflow is pretty much the exception [2].

I'm not interested in Markdown parsers which do not support tables. They are useless to me.

[1] http://www.reddit.com/about/ - "last month, reddit had 114,540,040 unique visitors"

[2] http://meta.stackexchange.com/questions/138946/can-we-add-ma...