Ok Rage, I just tested it with the help of Boon, I killed him in Gecko, which turned the place into a Combat Zone, logged off, waited 30 seconds, logged back in on the Same character, no Idle timer or Debuff. So you must have encountered a glitch, your IP changed via your router which can happen, or you perhaps were logged out long enough for your character to fully leave game, making it so when you re-entered your Idle timer reset.
My recommendation is to perform the same test with a friend, kill them in some corner of an unguarded town, log off, log back in after less than 2 minutes, and see the results, check your IP both times also. Do this without another character logged into the game no matter where they are, as it will effect the test. Because it is possible that it may randomly give the Idler debuff for however many seconds you have remaining of Idle timer from being logged out but still in game. If that is the case, than this is one of the things that Jovanka was talking about needing fine tuning. Because you shouldn't get hit with the debuff for being dc'd for a short period and coming back on the SAME character so long as IP didn't change and you didn't log in a different character in the meantime. It's a possible glitch that logging off but not being gone long enough to leave game, the game still counts you as "Logging into a Combat Zone." and gives you the debuff. I don't believe that is intended that way, again only for logging off and returning on with the SAME character.