Speaking to a regular down there last night and he was commenting on some of downwind crew kiting in close through the flagged area. He spoke to a couple of kiters about their performance but they said they didn't know they shouldn't.
I guess it's more about ignorance than common sense. Putting signs at the popular spots could be the way to go, showing where to and where not to.
At least people can't claim ignorance then. Doesn't solve the problem of doing downwinders through spots they've never kited before though.