Coaching is legit, the only time i can see it being wrong is if someone is unaware they are about to get c4'd.
Maybe you should stop rolling so much hmmmm, character is irrelevant just cause you character has a match up disadvantage it doesn't change anything to do with coaching.
It isn't just the match up, its the options that are taken away from the fight by having someone there telling you how to fight another person, and the match up then adds to it. Say someone is fighting a Ness using Marth, is it really fair that during a fight someone walks up and says hey you can standing chaingrab Ness. Its the fact that the fight is between 2 people and no one else. If the person you are versing doesn't know it before the fight, then it should be their mishap. Not to mention having to listen to someone else talking over your fight like a commentator, which as was mentioned before can be annoying for both parties.
At the end of a fight I try to tell who ever it is I'm versing, what to do differently if they fight that character again to help them along with what they do.
I know other people stand on this topic differently, but both Jaice and I have had it happen and it isn't just rude, it also puts off those new people who come to tournaments.
One of the biggest issues with these meets is that new people don't feel welcome, and I have brought a number of new people along each time to see how they like it and the first reaction is not a good one. If Jaice and I didn't like Smash as much as we do, we wouldn't have kept coming at the beginning either.
Also there is no need to personally down grade someones game ie, the rolling comment. The smashboards is about putting forward different views and opinions so as to discuss them and make for a better and more effective competitive scene for smash.