Still to my eye casual shirts look a bit strange without a pocket. In much the same way as I think a casual shirt without a placket would look strange. Just personal preference though.
I do think that OCBD and perhaps even BDs in general have some unwritten rules for their construction though i.e. placket, pocket and box pleat...
+1. I definitely prefer my OCBD shirts and my more casual shirts to have pockets, front plackets, and a box-pleat at the back - it just seems odd to go against tradition and to have them made differently.
Given the inherently casual nature of a popover shirt, I think that a pocket is appropriate.
For those people that don't like pockets, it's actually quite easy to remove them as long as you have a little "quick unpick" tool from a sewing kit or a pair of surgical scissors. Unpick the stitches, remove the pocket, give the shirt a wash and iron it, and any thread holes should disappear. I've done it on a couple of Borrelli business shirts that had pockets without any problems.