[smnc]

It is possible to disable kibitzing for a table (or a tournament, or a team match etc.), but kibitzing is a feature. It's often both educational and entertaining to kibitz high profile players and participate in the play commentary and banter.

The downside is that people can kibitz their own table (if kibitzing is allowed) using an alt account. Yes, it's a risk, but there are lots of ways to cheat online. It's trivial to cheat using out of band communication with your partner, as a sibling comment points out, or use a computer program to calculate odds if cheating without the knowledge of your partner.

So the whole thing is built on an honor system.