i never said it shouldn’t be used in bathrooms, maybe i should of said MR is no better than normal board rather than suitable. any plasterboard in a bathroom needs tanking in wet areas so its much better to use a fully waterproof tilebacker board instead if possible.
i have had to skim onto MR boards before, they are meant to have a coat of Bond-it on first to provide a key but the customer wouldn’t pay for it so it got skimmed without at his risk, was a few years ago now and i’ve never heard of any problems with it.
bigjohn unless epoxy grout is used all grout can let moisture through and can take a while to dry out especially in a heavyly used shower, i wouldn’t recommend using epoxy though.
mentioning new builds doesn’t mean much with the standards most are built to nowadays.