Most of those are solved with wrapping it in both <code> and <pre>, and #5 I don't think is even part of "ASCII art" anymore as it wouldn't be just ASCII anymore, but rich-text.
What do you mean? Add far as I know <code><pre> doesn't help with any of those?
Color is very much a part of ASCII art, if we consider ASCII to mean a broader range of different technologies. Just check the stuff in the article, or the stuff on https://16colo.rs/ site.
