Invented for Python documentation. Intended to read well in plain text as well as convert to various other formats including HTML and TeX. Reading well in plain text means that it can be more cumbersome to type than other plain-text markup languages.
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Pros
Pro Human-readable
reStructuredText is an easy-to-read, what-you-see-is-what-you-get plaintext markup syntax and parser system.
Pro Technical documentation
Without any adjustments RST has many facilities for writing technical documentation (API docs, syntax highlighting code, embed code from source files).
Pro Parsing from Python
Python's docutils include a parser for RestructuredText.
Pro Extensible
Generators such as Sphinx allow you to define your own custom roles, directives and output generators.
Pro It's standardized
There's only one standard to adhere to - no "flavors".
Pro Large collections of themes available
Cons
Con Setup can be tedious
If you prefer Python to stay out of the way so that you can focus on the task you are doing, you will find that overall Python just asserts itself far to much.