My understanding is that the Proxy is not valid if the proxy giver is present and voting. I've known a few cases where an owner has given a proxy to their lawyer or a relative to speak on their behalf but wanted to be there to hear what was said. They may even be able to speak.
This is what the Act says:
Proxy cannot vote if person appointing proxy votes
A proxy cannot exercise a vote in relation to a matter if the person who appointed the proxy is exercising personally a power to vote on that matter.
That section certainly says nothing about speaking at the meeting. The weird thing about this case was that the chairman ruled that the proxy wasn't valid but then ruled that the ownder couldn't speak becasue they had a proxy there. Talk about having your cake and eating it – it's that old strata custom of making it up as you go along (and then walking out of the meeting when you're challenged).