User blog comment:13th madman/7th Yonkou vote Nominations! DON!/@comment-24600241-20140206050341/@comment-4080028-20140206052405

As kind a gesture as this may be, and it is, I'm afraid Hiro's already nominated, so you don't need to nominate him again.

Likewise, you'd need three other, different characters to nominate alongside Kuroraka for your nominations to count. On the upside, you can still nominate one of your own characters as well. Just not Hiro. That was already done by Powerhouse, as you're well aware of now.