I wish this became a standard - plain text is great, but sometimes you do want style and formatting, and HTML mail is beyond horrible to get working across clie

I wish this became a standard - plain text is great, but sometimes you do want style and formatting, and HTML mail is beyond horrible to get working across clients (yes, I know there are a few well known templates, but still). I think the problem is that HTML and CSS are now so big, and people use such a range of device sizes, that writing clients to display things accurately and consistently is very hard. Markdown sounds perfect to fill the gap between HTML and plain text.