The question isn't whether important documents can be reasonably be represented as plain text. Clearly many can. The question is whether the typographical techniques listed are an aid in reading. And just as clearly, they are.
And just to note, Readability actually preserves bold, headings, breaks, and italics, while providing a different set of fonts and colors based on the user's preferences.
My bad on Readability, as I made an assumption without checking.
I see what you are saying, and I partly agree, but I am of the opinion that language is rich enough to emphasize relevant points without further aids. But it's becoming SO common to use _SO_ many aids that this is already standarized with two levels in HTML, namely the em and strong tags. How long until we need a third semantic level of emphasis? Of course, I enjoy freedom and choice, so assume people/the market must prefer your style by and large.
For the record, I know that italics typography has been used for centuries as an aid in emphasis. Still, I humbly feel this is an unnecessary artefact, which more often than not turns into a crutch.
I like how you went to ALL-CAPS because you lacked the ability to add proper textual emphasis and then that you felt the need for more emphasis still and again broke writing conventions to indicate you wished to add underlining. Made your case for plain text perfectly.
Buttons for clothing have been invented, pretending that my coat doesn't need buttons and then holding it together with my arms so I don't freeze doesn't make sense to me.
And just to note, Readability actually preserves bold, headings, breaks, and italics, while providing a different set of fonts and colors based on the user's preferences.