When referencing commits in the issue tracker, if that commit starts with a number the issue tracker will link you to the issue of that number and not the commit. (i.e. #7b5eac7 will link to issue 7 instead of linking to the commit 7b5eac7)
Opps. In the text when I didn't user number to prefix the commit I found that # should only be used for issues not commit numbers. My bad. Bitbucket is smart enough to figure out what text is referencing commits without needing a symbol.