Say that you train a priest in regular warcraft, his default ability is heal so when the unit is made heal is already put on autocast. I doubt it has any use for anything else besides this, or rather, i haven't found any use for it.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.