I did say that catching a players bad soul makes yours more good(sorry if it was confusing but i said it here:"you collect player souls that are good: your soul becomes more bad and vice-versa.(neutral souls don't change the soul type)")
Bad souls are something you do not want just on the term and the quality of the stuff you can get(for instance,I did not think of this till just now, if your soul is bad-you get less from the quest and you cannot trade souls for gralats at the little stor and the quality of what you can get is horrible/not stuff worth buying)(ignore this piece)