Also, in my experience heating the coffee in microwave increase perceived acidity even more. Which kind of make sense with this explaination as there could be pockets of superheated water when it is microwaved.
Could you try giving it a good stir right before putting it in the microwave?
Just curious, why do you think that would help?
Not the poster you're asking but they might have imagined the stirring being vigorous enough to keep the liquid moving during the entire heating period.