This simple program in literate haskell, using markdown in the comments gives unlit problems:

### Ok so lets try this again.

### A page that loads and compiles:

> myfact 0 = 1  
> myfact n = n * n-1

Lets see if it works!

If I run unlit and collect the output I can see where it went wrong:

$ ~/lib/ghc-7.0.1/unlit Main.lhs Main.lpp
$ cat Main.lpp
### Ok so lets try this again.

### A page that loads and compiles:

  myfact 0 = 1  
  myfact n = n * n-1

When I look through the source code of unlit.c I think the place to check for this would be here:

    if ( c == '#' ) {
      if ( ignore_shebang ) {
         c1 = egetc(istream);
         if ( c1 == '!' ) {
           while (c=egetc(istream), !isLineTerm(c)) ;
           return SHEBANG;
         }
         myputc(c, ostream);
         c=c1;
      }
      if ( leavecpp ) {
        myputc(c, ostream);
        while (c=egetc(istream), !isLineTerm(c))
            myputc(c,ostream);
        myputc('\n',ostream);
        return HASH;
      }
    }

It seems that cabal has a similar unlit function: http://www.haskell.org/ghc/docs/latest/html/libraries/Cabal-1.10.0.0/src/Distribution-Simple-PreProcess-Unlit.html\#unlit

I haven't tested it but, I think the cabal version would handle this case correctly (or be easier to fix than a C program from 1990). Would it be possible/wise/feasible to extract the cabal version and make it a permanent replacement for the current unlit.c code?