I have never seriously used Texinfo so I am just being theoretically here: What I like about Texinfo, when compared to other light-weight markup languages such as asciidoc, is that Texinfo has a DTD for its XML representation: http://www.gnu.org/software/texinfo/dtd/ . Hence one can easily check whether a Texinfo file is structurally valid. The DTD also helps when one is building conversion tools to other markup languages such as HTML and DocBook. The DTD helps me see if I have covered all the corner cases in the source language (Texinfo) when mapping to the target languages (HTML and DocBook).