I was under the impression that if you are marked as a dupe with someone (from public wifi etc) but it is clear that you are not the same person then it is ok. That is why Mu has the dupe status rather than banning people straight out. I assume Mu has his own criteria for when it is clear or not that two dupes are different people.

you have to be careful with wifi and playing from your phone. many smart phones will access an available wifi network instead of the mobile phone network (in the states) unless you have the wifi function turned off on your phone. i've been burnt by this. it's not fun. hopefully it goes away after a bit...