When installing a new Moen widespread 2-handle faucet, we (stupidly) reversed the hot and cold water bodies. Is there any reason we can't just leave them like they are?

remove and turn cartridge 180 degrees then re-install

Easy one.
Feel the pipes. The pipe on the right should be cold. If the pipes are correct, turn the cartridge 180 degrees.

You bought two cold water faucets. The threads are reverse on the hot water faucet. Exchange the wrong one at the store you bought it from.

hello, this can happen if the shower body unit was installed incorrectly, the installer connected the hot to the cold side and cold to the hot side, what you can do might be a bit difficult but the water supply lines are reversed you need to open up the wall and attach the cold and hot lines to the right sides.. hope this helps

these valves can be adjusted by removing the handle and adjusting the white gear that regulates the hot and cold that come out, try going more to one way if it gets colder then go the other way.

you may have deposit's,(mineral) in water way's. maybe piece of cartridge came off and blocking water. try removing cart' and inspect brass valve body,to see if any thing is there. check cartridge as well.

Hot water line connected to left side of faucet? Did you replace tap set, or just cartridge? Cartridge may be out 180 degrees.

You turned the faucet body when you tightened faucet you need to loosen and reposition body so handle goes left and right equally and retighten while making sure faucet body does not move

You can try to rotate the first plastic ring to the left of center a few teeth, this will let the handle advance alittle more to the hot side.

tun off the water.
unscrew teh allen screw under neath the handle. pull out hteh handle. undo the wall plate and gain access to the cartridge in the handle body. turn the artridge around 180 degree and reisntall all parts.