For a while now my text editor of choice, Geany, has supported syntax highlighting for Markdown. But I had to select it manually from Document > Set Filetype > Miscellaneous Languages > Markdown source file. A bind indeed.
Today I found that the file extension .mkd brings on the syntax highlighting automatically.
I have also been using the plugin Markdown for WordPress & bbPress in WordPress (see screenshot) and it’s a pleasure to work directly with Markdown rather than have to be constantly converting, using the Showdown converter.