AsciiDoc was implemented in Python. AIUI, the project got neglected or abandoned, so someone re-implemented it in Ruby to create AsciiDoctor -- same markup, different rendering engine.

Some like it, some don't. I don't mind working with it, but I haven't used it in anger. It seems pretty good. It's richer and more expressive than Markdown, which is feeble and that's resulted in multiple subtly-different, incompatible implementations.

It compares with RST -- ReStructured Text, another lightweight, human-readable plain-text markup format that's used in several places.

The advantage of ADoc is that its model maps onto that of DocBook, so it's possible to render ADoc into DocBook and then use it with established DocBook toolchains.

I mostly work in DocBook, but I don't like it much. I personally find raw XML horribly wordy and it took me a long time -- at least months -- to learn to read it or write it fairly easily and fluidly.

ADoc you can learn in an afternoon and the source remains perfectly naked-eye readable.

The arguable weakness is that because DocBook is a tightly-specified format, you can formally validate a DocBook document. You know it will work and render to something, even if what comes out isn't quite what you wanted.

Whereas you can't verify an ADoc document. It's possible to write something that looks fine but isn't and which might produce wildly different output from what you intended. You just can't formally tell (i.e. in software) if it's going to work or not: anything will work and produce _something_.

An advantage for humans, but a big snag if you're trying to automate making PDFs or e-books or something from it. In most cases, if you're using some form of continuous integration or something, it's preferable that it will stop with an error and tell you than for it to churn out something totally bogus.