There seems to be a split between those who say the backer board should go over the tub flange and those who say it should go above. Those who say over say so for drainage. Those who say above seem to suggest because of the surrounding drywall plane.
The tile expert forums go with it over the flange; seemingly the general contractor forums suggest above. Most forums suggests a vapor barrier even with Hardi Backer.
How does a person make the right decision with so many conflicting viewpoints? I know in other posts, the two options are covered; however, little is discussed with regard to the problem of going over the tub flange causing the drywall plane to be uneven. Shimming for example over 1/4" would seem to be a problem blending the CPU board with the drywall. How is that done successfully?