The detection system has seemed really weird for quite some time I think. I do remember hearing from trustworthy forum members that accounts get flagged for being used on multiple IPs. It's quite annoying since it makes perfect sense to be in a position like the one you described!
Lol that guild must be funny. That's very awkward that someone was that desperate for neopoints, maybe they'll get silenced so they can't beg anymore haha!
Then again it'd be weird since it has been months since he last used the account so technically it has been used only over 1 IP address in the past time.
It is ineed annoying but they didn't do anything about it yet, and then again, would be weird. It is really easy to even manually change your IP address, and sometimes without your choice, your IP changes. (My laptop and my bf's wifi do not like one another and his router somehow deletes my laptop from the IP list and randomly gives a new one when it feels like it too). I haven't had any trouble with it and it's been two years since I played like this. I doubt it raises a red flag somehow. More logic would be to me if like, you play over 1 or 2 IP's all the time, and suddenly for one time, a different one is used, then the old ones again etc. But if the IP changes all the time, I'm not sure they could make a thing out of that.