If it's an attack-boosting spell or something, I would suggest remaking the ultimate to add an aura in a disabled spellbook. The buff will be removed, but you'll still have the aura, and it should refresh itself in a flash.
Add to your Initialization trigger:
Set PurgedSpells[1] = Stunned
Set PurgedSpells[2] = Slow
Set PurgedSpells[x] = x
Event:
A unit begins the effect of an ability.
Condition:
Ability being cast is equal Purge.
Actions:
For each (Integer A) from 1 to x do (Actions)
Unit - Remove PurgedSpells[(Integer A)] buff from Target Unit of Ability Being Cast.
If your removing auras then thats a different story and if you have many spells that you want to remove i wouldn't suggest this method. Also this would require the purge spell to be targeted.
You can refer to the number of spell steal priority. Normally, Buff will be remove because of the spell steal number. If you put the number of spell steal priority to zero, it might not be removed by Abolish Magic, Detonate and also Purge. try 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.