My friends and I have used each other's computers to go on mibba. I think it just means more than one account for the one person. It's more an ethic thing, seeing as though they don't have much to prove it. And if you used the same computer, how could they tell? Unless it's using it at the same time, like, one window open logged in as one person, and another as someone else, I'm not sure if that works. I don't think it does.
Normally, Dujo can considers same IP address same people. So if like you and your sister or something wanted separate accounts, you could message him and explain the situation so you don't accidentally get deleted for being suspected of having multiple accounts.
And if you used the same computer, how could they tell? Unless it's using it at the same time, like, one window open logged in as one person, and another as someone else, I'm not sure if that works. I don't think it does.