"Christopher Nelson" wrote

My master bathroom and walk-in closet share a wall, the wall behind
the vanity. I don't know what the original owner was thinking but
above the 36", single-bowl vanity there are 3(!) double outlets. One
is in a 2-gang box with the switch for the light above the sink. The
other two are at the other end of the vanity in their own 2-gang box.
It's overkill and it's ugly.

New faceplates can help a good bit there.

I know I can't take out the extra outlets and bury the box but I'm
contemplating cutting into the closet wall and just flipping the box
around so that the outlets (or a blank plate) face into the closet
then patching the plaster in the bathroom. Is there any code or
safety issue with this plan? (I know code varies slightly from place
to place. I'm looking for a general answer.) TIA.

I would do this. See, with 4 left in the bathroom, thats 4 more than I have
(grin, no outlets in any of my bathrooms, older house built before folks
thought they'd need'em). 4 works well and is more than most people have.
The only time I see 3, one of them is located down lower on another wall and
used to run a spare (bathroom safe) heater in cold climate places.

Now, adding an outlet to the walk in closet is a benefit if it doesnt have
one. It provides a spot to run a hand held clothes steamer, hang an
electric rechargable small vacumn cleaner, all sorts of things.

Were I buying your house, I would be more attracted by the ability to plug
in 4 things in the bathroom and 2 in the closet, than 6 in the bathroom and
none in the closet. I may be weird though! Depending on the shape and size
of the walkin, I'd be delighted to find a wall mount flip down small touch
up ironing board and an outlet right in there with a wall mount iron holder
(safety design, they make them for this).