I've updated some of the information on Anvil Displacements tab (http://dev.wallworm.com/topic/44/displacements.html).
I also added a new article altogether on Understanding Wall Worm Displacements (http://dev.wallworm.com/document/122/understanding_wall_worm_displacements.html) .
I've updated the docs linked above as well as added a new video:
New tip:
When using the PolygonMap plugin on a displacement, make sure that you have the Weld, Quadrify and Group options on. If not, you will get incorrect UVs on your displacements once exported to Source.
Also, if you ever unwrap your displacement (which you should not) then you need to make sure that all interior mapping edges are stitched. If not, again you'll get incorrect UVs.