No longer considered investment. Now considered taxable income.

To me this is a big deal and a lot of miners forget to account for this as the tax amount can be fairly high at 30 percent or more depending on your tax bracket.

I think in this scenario it's okay. He made 2x gains, He didn't cash out he borrowed and use his coins as collateral. I don't know what rate he's paying but I know maker Dai borrowing fees went up high at 16- 20 percent credit card levels.

So he still has skin in the game for more upside without getting left in the dust mining at higher difficulty if price rise.