Therapists are said to have good boundaries if they avoid things like excessive self-disclosure, dual relationships, inappropriate touch, and too much contact outside sessions.

But therapists trample other boundaries and nobody blinks. Examples: expecting trust without earning it, failing to explain risks before rummaging thru your psyche, pushing you to expose yourself while they observe voyeuristically, collecting your intimate disclosures and secrets while keeping theirs largely hidden, interpreting your thoughts and behaviors sometimes aggressively, giving life advice, behaving ambiguously, withholding important information.

Not saying all therapists do all of these things, but most of this is codified in the literature.

These things are commonplace in therapy and thus people are told it's perfectly "normal". But in any other context they would likely be considered violations of personal dignity and autonomy.

Therapy is claimed to help strengthen one's interpersonal boundaries. But as someone pointed out, in fact it can be an exercise in having your boundaries systemically broken down. For me it was.