@codinghorror has blogged about markdown at The Future of Markdown - a worthwhile read.
I think discourse is encouraging people to join the discussions at http://commonmark.org on improving markdown and making it more consistent for everyone, including discourse.
The commonmark spec CommonMark Spec actually describes “intraword emphasis” which is what @JazzyJosh is complaining does not work in discourse now, so maybe this is indeed a bug.
Personally I don’t see intraword emphasis as much of a priority, and I also don’t see the toolbar in the editor as much more than a guide. I always end up manually tweaking the markdown it generates.. which I think is how it’s supposed to be used.