In my defence, the comment I was replying to mentioned "renderers" and "converters". Furthermore IMHO, any text editor is a Markdown reader. If you want it formatted as is it were "markup" then might I suggest converting to e.g. PDF using Pandoc and then using one of the many capable viewers.
I see your point, and maybe it's a matter of preference, but I really do use my text editor for reading Markdown. I wouldn't do the same for a Word doc or HTML, without at least running it through a convertor first.
