Sure, but if we could paste HTML between editors and browsers without any rendering or layout issues, there would be no reason for users to look beneath the surface. I do agree that we're not quite there yet.
Why are people still interested in Markdown - what problem is it solving and for whom?
It's 2012 and we have HTML 5 compliant WYSIWYG text editors. We no longer have to write plain text littered with special codes, for the purpose of running through a parser, to produce HTML which looks nice on a web page. Maybe it made sense a decade ago when web forms had terrible editors, but not anymore. I think Joe Internet writing blog posts and forum replies would agree with me.
For developers, a README file in plain text looks great everywhere, and avoids any Github vs Bitbucket vs Assembla display issues. If you need to write structured documentation for a system, there's probably already a designated markup language you're supposed to use, so Markdown doesn't help there.
http://www.f-secure.com/weblog/archives/00001777.html
http://blog.reddit.com/2009/09/we-had-some-bugs-and-it-hurt-...