It's standing policy at Party.

You will both show up as the same IP, and if you try to sit at the same table, the system will give you a pop-up saying you're already at the table.

If you join the same tourney, but at different tables, they will let it fly -- but that certainly gets awkward if you both progress to the same table, and some other players have a big problem with it. It's hard not to coach each other when that happens, and card-sharing is almost inevitable ("No, honey, I folded an ace!")