I'm assuming you either have your splash damage done with a search effect that runs a damage effect or just simply a single damage effect. Either way, search for a field in the effect called target filter. Uncheck the allied and player checkbox(So that only Enemy(and possibly neutral, if you want that) is checked).
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.