Apart from the obvious solutions like MS Word, there are many systems that accept the simple (plain) text along with formatting markup. Some of these like Groff are historical, but others like AsciiDoc are rather new and in active developoment. If you do not do much more than dividing into chapters, the markup itself seems trivial to learn. I used them for technical documentation at work.
The proponents of these systems say that writing just plain text allows to concentrate on the text itself, not formatting and presentation that a "user friendly" editor immediately requires from the first word. Also, there are multiple versioning tools that would work well with plain texts but not with the binary files of the usual text exitor. These tools, normally used by software engineers, allow to compare past and current versions side by side, create and merge branches and things the like.
Because of these potential advantages, I started to think about using one of such systems for my creative writing projects. To help me with this decision, I would like to know if any notable writers have used such systems recently, or if there are any notable pieces initially written using them (by the original author, not by the technician in the process of preparing the publication).