This doesn't quite follow on from your point but I still like using plaintext and emphasising using asterisks etc. in mail. Firstly, my mail client messes up with them. Secondly a mail client that actually works correctly like Outlook tends to bulk out massively with HTML (because that's how it's represented). Swap a few dozen of these HTML emails with a colleague, then look at the source and you can sometimes see it exploding into megabytes, which might render correctly (in Outlook anyway), but it certainly offends my programmer sensibilities of efficiency.