Voting for your own bug confirms it (changes status to NEW). You can not confirm your own bugs. As simple as that.
While I generally agree, the "status-changing" is an effect a number of bugzilla-users (especially new ones) are probably not aware of. Documentation helps here (on the voting-page, for example). Also, not counting votes from the bug-submitter could probably be patched into the software? There are some options, but invalidating valid bugs doesn't help wine imho.
Regards,
Wolfram