Karma aside, flooding the comments with a chosen narrative via army of bots seems like it's already happening. I suppose the bots can also do voting rings, but they don't necessarily need to.
Would be interesting to see "fastest growing accounts in last N months" or something similar. I'm guessing the ones that are actually humans would be closer to the top than the bottom, but maybe HN users aren't better than the average person to detect AI or not.