Thanks, folks. I was misinformed by the guys at Netscape. I
thought that support was native, so I suspect that, judging
by the source, this may be supported (however so) by
WordPress.com with or without enhancements.
Yes we do support it in WordPress.com, and the syntax has been very
popular and easy for people to use.
For WordPress similar functionality would be nice, but it'd probably be
better left in the realm of a plugin. (Perhaps we can pluginize the code
we use on WP.com.)