As I explained in your other thread, you can't use your reaction for two different features. You need to take your pick of which feature to use for your reaction. So no, they can't stack... not from the same source that is.
If you had one character use his reaction to use Spirit Shield and another character used it to use Interception, then yes, both effects would stack. You're simply limited to one reaction per round.
I think I know the answer but I want to double check...
They don't or can't stack? You have to pick one OR the other that you want to use as your reaction?
As I explained in your other thread, you can't use your reaction for two different features. You need to take your pick of which feature to use for your reaction. So no, they can't stack... not from the same source that is.
If you had one character use his reaction to use Spirit Shield and another character used it to use Interception, then yes, both effects would stack. You're simply limited to one reaction per round.