I thought a goal of Markdown was to be a set of conventions that were readable on their own as well as being transformable to a rich text/HTML representation.
You can read a Markdown document pretty easily using "less" or any other character-based interface.
The same is not really true of reST.
Maybe I'm confusing that with some other plain-text markup convention?
all of that is true, but markdown targets HTML as its "native backend", if you will. it is not feasible to render markdown -> pdf without having an intermediate HTML representation.
this is clear from the fact that HTML can be inlined in a markdown document; this is part of the spec (in so much as there even is a "spec" for markdown, anyway).
reST is also designed to have human readable source. You might not like it compared to markdown but it has to serve as a the docstring format of Python and does so fairly well.
You can read a Markdown document pretty easily using "less" or any other character-based interface.
The same is not really true of reST.
Maybe I'm confusing that with some other plain-text markup convention?