The CSS used for Bitbucket's site has a tendency to impact rendered ReST files when the section headers in the ReST happen to match up with selectors used in Bitbucket's design.

An example can be see at https://bitbucket.org/jayclassless/memcacheinspector/src where the "Introduction" section of the rendered README.rst has a dark blue background (today, at least; a week or two ago, the background was white, but so was the text).