I disagree with the nether being "hacked" by someone who was able to pass the boundary on purpose. If this were true, why didn't they break other maps, like planetoids or the traditional map which are much easier to get past the boundary?
The logical conclusion is that someone in the overworld made a nether portal outside of the nether boundaries. Since nether gates travel 8x farther in block travel versus the overworld. My conclusion with the evidence is that someone placed a nether gate directly at the border of the overworld, or near it. This could have occurred from a mistake by someone living near the border making a nether gate, or by potentially intentional actions of passing the nether boundary using this "glitch" method.
I will attempt to replicate this in game with you, if you have the time.
Two solutions:
1: Make the Nether borders 8x the size of the overworld 3100 block size. 24,800 map size.
2: Remove the nether, give everyone nether kits all over again.
The logical conclusion is that someone in the overworld made a nether portal outside of the nether boundaries. Since nether gates travel 8x farther in block travel versus the overworld. My conclusion with the evidence is that someone placed a nether gate directly at the border of the overworld, or near it. This could have occurred from a mistake by someone living near the border making a nether gate, or by potentially intentional actions of passing the nether boundary using this "glitch" method.
I will attempt to replicate this in game with you, if you have the time.
Two solutions:
1: Make the Nether borders 8x the size of the overworld 3100 block size. 24,800 map size.
2: Remove the nether, give everyone nether kits all over again.