The high/low seating doesn't seem to be too much of a problem. When the decision to move indoors was made, it was announced at venues. This would have been OK if people had been at the venues and been willing to leave to go grab a spot indoors.

Somebody once explained the etiquette of the huge tarps to me. They had a huge tarp and the ground was dirt. They spread it out and had a spot to sit, plus room for others. If there's room on a tarp, it's fair game. The people who told me this had one of those tarps, and I sat with them for that concert.