Some great advice!! Too often, parents think they're entitled to be in the corner of their kid. And as Will suggested, often times they are not the best "coach" in the corner!
I urge all parents, to find a coach your kid will listen to, and have them in the corner. That way, parents can be the support system they should be.
Also as Will discussed ... we often get the misconception that "coaching" is done matside. I am among those who think we place far too much emphasis there, instead of the practice room!