You need either a) be present when the +v is granted to an op, and you will still see that he isvoice, or b) the network that has multi-prefix supports (CAP +multi-prefix, or NAMESX protocol extension) so that you can see both status prefixes when you join a channel.
Make sure that you have upgraded to the latest version of mIRC, v7.55, in order to benefit from the above features.
