This feature is not so easy to implement, yet it is possible as a plug-in which you could install on sites where it's necessary.
Speaking of cotonti.com in particular and similar sites, I would prefer Markdown over HTML as it is more simple than bbcode and not so junky as HTML. We can start using markItUp with Markdown for new pages on this site at any time, but all our existing pages are in HTML and cannot be converted to markdown. The same is true for forum posts, except for the bigger problem: we cannot use several types of markup in forums at the same time, all posts must be in the same format. So we can't use markdown on forums.