In the past, I have given advice via Twitch, received advice via Twitch, and shared advice live via Skype. I now think I was wrong to do so.
First, what changed my mind?
I had heard discussions in the past (including @Smmenen and @CHA1N5 excellent podcast So Many Insane Plays) about players playing as a team rather than a single player. The conclusion they seemed to come to, and the one I accepted, was that it was potentially unfair but worthwhile for the community benefit and the production of subsequent content. You can't exactly stream Magic and interact with your chat room if there is a rule against live assistance, for example. Today, I placed 4-2 in the Vintage Power 9 Challenge while streaming the event. After I wrapped up the Swiss, I considered watching any Top 8 streams still active. I saw that both @Brass-Man and @The-Atog-Lord had made Top 8, and both were playing with a team of players rather than a single player. One of the flimsiest justifications in favor of this practice - that it doesn't provide that much advantage, as the primary player has to expend additional energy and concentration dealing with spectating players - is no justification at all if multiple players giving advice actually promotes successful play. I was and am upset that I lost one of my matches (which I thought was a heads-up match against an excellent player) to a team of players working in concert. In my opinion, 1v1 Magic play is supposed to be a contest of two individual players, not two teams of players. In paper tournament play, there are "outside assistance" rules which forbid exactly that. In MTGO play, that rule does not exist. I believe it should.
I think multiple players controlling a single account and competing against a single player is obviously unfair.
I think the rules should ban whatever is unfair, either by general categories or by specifically naming different actions.
It would obviously be unfair to make the rule retroactive. Andy, Rich, and others should not face a penalty for actions which were legal at the time they were taken.
The fact that in some cases multiple people can control a single account without being detected should not prevent forbidding the practice. Consider cheating - no player would argue that card manipulation should be legal just because some players might get away with it.