It's definitely cool when mags split. I had one that began to split, but never finished up on its own so I ended up cutting it. By the time I cut it, both sides had mouths and were eating independently.
Some mags split down the middle from the mouth, where each side has half a mouth which close up after the split. Others, like the one I have literally split in two where a second mouth forms from the original, then the nem splits into two separate nems.
I felt like I had a two for one deal too!