I wondered the same. It can’t affect the taste. Is it a principle thing? I boil a kettle on a stovetop every morning for coffee I make in a French press because that’s how I like to do it, but I’d microwave a cup of water for tea in a pinch.
Also don’t really trust the hot water from the tap. Idk why.
It really _does_ affect the taste.
I suspect it's because boiling water in the microwave takes less time and doesn't induce convection currents so that the water retains more dissolved air than when boiled in a pot or a kettle, but that's just my personal theory.
(Re-heating a cold cup of tea in the microwave is fine.)