The problem with using your Bitbucket username is that it is often the case that other users can commit as you or vice-versa. It is often the case that a local username will be 'david' and this has caused a lot of commits to be misattributed on Bitbucket in the past.
The solution is to change your mercurial commit string or to alias as you have done.
Sorry for the trouble,
Issue #3314 was marked as a duplicate of this issue.