Could you please make golden pig map private for each one? ending up with a mage or DrK (or anyone else who can steal kills easy) is really hurting the rest of us without it. I see no reason why we should share the map with others on a limited time frame. if not that, you could at the least put all of the above mentioned jobs in a map of their own.
The server does check if there's already someone inside. In some cases (like yours), another player in the same channel clicked on the compass at almost the same time as you, which explains why you both got into the same map. We also checked with official sources which shows that it's intended to work this way. As this is a v83 server, there's no concept of "instances" map like in the latest version, where each instance of the map is created for each player (i.e. 1000 players click the compass, 1000 instances of the map created). So if we were to even attempt to solve this problem (which is quite minute. Just don't use compass in channel 1 to reduce that risk), we would have to duplicate the map, tons of it and that means new patch, and increased file size. So in general, I don't think there's any viable solution.
What Kai says is correct, however there was an issue with the Golden Compass where it failed to properly check if a player already was in the map, that has now been fixed.