For some reason, it doesn't, despite the fact that Silence works on all spells and the D&D rules say it should. Could that be changed here to make Thunderstones, Deafening Clang etc useful against divine casters?
Being deaf and being silenced are totally different. The reason people can not cast in silence is because they can not speak. Deafening clang and thunderstones simply make them unable to hear, I believe?
I think Egon's referring to chance of spell failure (http://nwn.wikia.com/wiki/Deaf). In which case, that is a bit weird.
According to NWN Wikia, being deaf (//%22http://nwn.wikia.com/wiki/Deaf%22) causes 20% arcane spell failure. The d20SRD indicates that deafened (//%22http://www.d20srd.org/srd/conditionSummary.htm#deafened%22) causes (in D&D rules-as-written) a blanket 20% spell failure.
But deafness is an NWN effect. We cannot change what effects do. We would have to look up all instances of deafness being applied in scripts, and add in an extra spellfailure effect. This could lead to inconsistency in what happens when you're deafened in EFU:A, if we don't find every instance.
It seems like a lot of work for something that no one even knew about, and I bet few people care about, either.
This shouldn't have anything to do with Silence, though.
Ah forget it then. I didn't know if it was a hard fix or an easy one. :P
Most commonly you'll be blind and deaf at the same time, which is worse then spell failure because you can't target well, or at all.
Ah, I never knew about that 20% spell failure on deafness.