Popped another one today, the fifth broken spoke on the MTB's stock rear wheel, less than a year old. Luckily drive side this time. Haha, I'm much more confident in removing and reinstalling a freewheel than a disc brake rotor. The first time I broke spokes on this bike, I tried to remove the rotor but could not and had a shop replace the spokes. Since then I've purchased a better torx wrench and have successfully replaced a non-drive side spoke.

I think I should replace the wheel. There is something wrong here. I do put my bikes to the test, but it's very unusual for a bike to fail the test so often.