It seems like something should have happened to him after the Kolhii ball incident. I’m not saying they should have sent him to The Pit. I’m just saying they definitely should have sent him to The Pit for his various crimes.
After the Bohrok Kal were dealt with, it is implied that Ahkmou was kept under close watch:
As for why… Only Greg can ultimately answer that, but a possible answer might be the fact that the Matoran were dying left and right to everything for a thousand years, and anything harsh enough to put him out of the way for good (including the death penalty) would lose them a valuable pair of hands, and Ahkmou was an exceptionally skilled carver.
That is a fair point. It’s just that I don’t see how him being a good carver would justify his continued presence in Po-Koro especially since he had been engaging in what could be considered Biological Warfare against his fellow Po Matorans.
From Reign of Shadows:
“We should have killed that lousy traitor long ago,” Macku muttered.
Every Matoran remembered Ahkmou’s crimes on the island of Mata Nui, involving the sale of Kodan balls tainted with Makuta’s darkness. Many had heard the tales of his sins on Metru Nui as well, in the weeks before the Great Cataclysm. Although he had largely kept to himself for the past year, no one really trusted him. But Turaga Vakama insisted he not be exiled. “Better to keep a doom viper beside your bed than to let it wander free. At least then, you will know from which direction its strike will come.”
That makes a lot of sense actually. Don’t know why I didn’t think about that.