If you use vim as your primary Markdown editor, I'd suggest plasticboy's markdown plugin: https://github.com/plasticboy/vim-markdown

I was using vim's default syntax highlighter for Markdown and ran into highlighting issues with unclosed single quotes.

Since a lot of Markdown files use .md instead of .markdown, I'd also suggest adding the file `~/.vim/ftplugin/modula2.vim` containing:

    setlocal filetype=mkd