Practical Unix Manuals: mdoc
I love man pages they are often easy to read, but roff is not that easy to author. So it nice to see good documentation being posted.   .Sh SYNOPSIS 
   .Nm 
   .Op Fl C 
   .Op Fl o Ar output 
   .Op Ar prefix

becomes this:   SYNOPSIS
   hello	[-C] [-o output] [prefix]


Semantic formating is nice, but atm I'm not sure there is much value to write the above vs using markdown and just convert it to roff.