I think we do need to consider the difference between "soul" and "mind" (for lack of better words). It seems to me that while the soul may be able to survive and reincarnate, the mind is what gets dissolved in the Life Stream after they die.
So the Ascians we captured with auracite, their souls may have survived, but their minds - containing all their memories and knowledge - would have been destroyed.
Normally the soul and mind would be tightly attached to each other, so Sharlayan scholars and the like may not have noticed that there are two different parts.
The soul, I think, would contain the basic core of personality - so a reincarnated person would be similar but not identical in personality to the previous person having the soul.