As someone who has a couple rigs mining 24/7 I would say he’s looking at the profitability of mining wrong. Personally I don't reinvest my mining profits in more mining equipment. There's a hard cap on how much amperage can be delivered to my house, and I have no interest in interfering with my daily appliances.
As far as when does it becomes profitable to play games with consensus? Never. Most miners mine using pools like suprnova, ethermine, and nanopool. I don't have control over whether we are appropriately confirming transactions or not, but it would be pretty unwise for my pool to start violating consensus.
As far as when does it becomes profitable to play games with consensus? Never. Most miners mine using pools like suprnova, ethermine, and nanopool. I don't have control over whether we are appropriately confirming transactions or not, but it would be pretty unwise for my pool to start violating consensus.