LOL...
when you do normal spell, the unit in question have a little icon to say they are targetting.But when you do a custom spell, they don't have it.
To change that you just need to go in buff editor (right side of ability editor) and search what buff you use (or create a new), when you see it, just change the icon and change more things if want.
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.