Just some facts from me.
First account about lvl 25 banned with proxy ipvanish ON (account registration from proxy too).
Next account about lvl 15 banned yesterday with using my home IP.
I have some char's from another computer with same ip that is not yet banned about 25 lvl.
I am use only one active char at time.
So i think that they can mark computer and they don't care about proxy you use at all.
If your ip or machine are already marked they can easy ban you again. Also they ban only online accounts.
I guess all this systems are script based and fully automated. The GM's just check already banned char's or prepared list for ban's that all is correct (like bot chains, quest finished or mobs killed) or maybe select some char's and port them to GM room.
Some lighthope's GM's can easy read this forum and this thread like all of us. And then can use bot too to see how it works and improve there scripts.
The only way now is more tests about your config. If you already banned what methods are you used and what you have tried?