I upvoted your response as your ideas are very reasonable but as for me, I don't like e-mail for a number of reasons, both psychologically subjective and technical.
The first things the e-mail ecosystem is to do to become more adequate to the modern day world are to deprecate all the codepages but UTF-8 for any part of a message (header included), eliminate the overquoting tradition (including full text of the message the message is a response to) and introduce an efficient thread tracing mechanism instead, establish a more reasonable signature culture (i.e. people and software to stop including redundant and useless information in the bottom of every message) and make Markdown a core part of the standard (while HTML should better be deprecated).
Those are all very good ideas for email. Part of it could be dealt with in RFCs, part of it by changing default email client behavior.
I also agree that email should be a personal preference. I think that DFeed[1][2] shows how open discussion systems should be built. DFeed provides a unified discussion system that is simultaneously accessible through email, NNTP, a web interface, and Atom feeds. That would be a really nice way to offer a comment discussion system on a blog.
The first things the e-mail ecosystem is to do to become more adequate to the modern day world are to deprecate all the codepages but UTF-8 for any part of a message (header included), eliminate the overquoting tradition (including full text of the message the message is a response to) and introduce an efficient thread tracing mechanism instead, establish a more reasonable signature culture (i.e. people and software to stop including redundant and useless information in the bottom of every message) and make Markdown a core part of the standard (while HTML should better be deprecated).