My son and myself have our own pc and version of warband running off the same router.I believe this will give us slightly different ip's anyway.I dont really see what the problem with someone having 2 versions anyway,unless they are banned on 1 account or are using both accounts at once to leech from a dead server.But I suppose they are the only 2 reasons 1 person would have 2 accounts.
Personally I dont even use my alts as I consider any use of alts is xp my main charactor missed and longer it will be untill they go up a gen.Rarely I will use a skip the fun charactor just to test an idea,but that would only be for like 10mins and i havnt done that for months.