There are not really hard and fast rules about what therapists can talk about to their clients, so much as the guideline that the focus is the client, and whatever countertransference or personal disclosure the therapist shares should be for a purpose that is designed to help the client. It can be helpful to the client that the T is willing to be honest and open about the T's philosophy or understanding of the problem (or not, depending on the client's needs). It could also be useful for a client to understand that interaction with them can tend to be confusing, and then to explore why people, not only the T, might be feeling confused in some interactions. Countertransference can be useful because most likely the T is not the only person who reacts to the client that way, or because it can lead to insights that might help the client to understand himself or herself or the problem that is to be treated, etc.