I don't know about BitBucket's particular flavor of Markdown, but for a full-featured Markdown, see [Pandoc](http://johnmacfarlane.net/pandoc/). It supports the elements you're probably missing, ex. definition lists, tables, LaTeX math, footnotes. To add a line-break, it supports using a backslash instead of trailing spaces.

Also, Pandoc gets deeply-nested lists right.