I think that sometimes, a T disclosing something painful from their past can help to bring them closer to a client, and show that they can relate to what the client is going through. But, it only works sometimes. The T needs to be able to choose whom they disclose things to very carefully.

My T has never disclosed much of anything other than basic info to me...she knows that I would empathize too much and want to help her instead of focusing on me.