For what it's worth, I don't have a horse in this race. In no way will I benefit from what I am proposing, because I don't play Pathfinder as a PC. I am strictly a GM and have spent a total of maybe 5 hours on the player side of the screen. I am a generally inclusive, not exclusive, GM and I don't run PFS. The RAW, as I see them, are what I adjudicate at my table.
I strongly believe the descriptions of supernatural abilities wholly contain the limitations on what a supernatural ability can target. If line of sight is required, the supernatural ability says so. Otherwise, I use what makes the most sense. Charm, Cackle, and whatever other hexes require the target to hear you, don't make sense to require line of effect. As long as you can hear the ability you should be able to be targeted by it. That is, after all, how the supernatural bardic performances work.