Highly disagree with most of the points here, except for the Obiton one.
Using darker colors can look very nice but has to be done right.
Font's smaller than size 4 have their use as well, especially since letter sizes can differ from font to font and saying it is bad on ALL of them is not true.
4-6 Lines thing.. also debatable. Using a certain amount of indent's or a pi amount can very well result in texts with a size of 6+ lines that are easily readable and forcefully putting tabstops in your texts can end up making them harder to understand, which is the opposite of what you want.
Overall though I suppose if you follow all of the steps that you have listed here, you are going to make sure that everyone can read your comms/stories/whatever while they won't look too bad.
