It might not be a single person, but who knows. I've been fairly confident that whole families engage in bounties, sig campaigns, and whatever else, and there are probably community bounty farms whereby all the members pool their funds together into one wallet. But in the end, it's impossible to say what's really going on when you find crap like this. When accounts are tagged, you'll start hearing all sorts of excuses and pleading--but there's just no telling what the truth actually is.
With this many accounts, though, I doubt it's a single individual. Possible but unlikely.
If signature campaigns is their only source of income. such people will do anything possible to earn a decent amount here, they have all the time. I have a sibling whom i trust so much and is sometimes active in the forum but we have never shared a single address. Hell i even don't have access to any of his private keys and he doesn't have access to mine
What is peculiar about these accounts is that they apply in the same signature campaign one after the other on top off sharing addresses from the same HD wallet.