I unchecked it after restart and it had no effect. I started Input Director last but achieved the same results. I forgot that HotkeyNet was targeting a direct window in the cases other than Vent which explains why they still receive the events. Targetting Vent directly has no effect, probably because it reads keys in the way you stated above. It's starting to make sense.

But while cooking I had a new idea...

I can move Vent to my Slave and use HotkeyNet to send the hotkey to the slave instead. The Slave keyboard is not blocked while the Master has the focus of my Master keyboard, so Vent should still receive the event, and when my Slave has the focus of my Master's keyboard it should send directly anyway. I think this will work... there's only one way to find out. I don't care which system I have to use for Vent so long as I can talk while using either.