Markdown in READMEs not working?

I've tried to use markdown as my markup language of choice. But I couldn't get Bitbucket to render it correctly. All combinations I could think of (preamble on top, in second line, as Windows file, as Unix file, preamble after the first heading, renaming the file to README.markdown) did not work.

Bitbucket always shows the text als non-formatted. It does however recognize that I changed the format (since my README is not displayed as pre-formatted anymore), but it does not compile my README. And I have no choice of seeing the error. Online markdown parsers had no problem parsing my file, is Bitbucket maybe more strict?

My test project was webvariants/varisale, but I will be stripping the test commits soon.

Greetings,
Christoph