What are some signs that a therapist may have poor boundaries with their clients?

Disclosing feelings, fantasies, and experiences to the client in ways not related to the work the client is engaged in.

General Introduction to Boundaries from Panahi Counseling:

Failing to mention the client in supervision/consultation, out of fear the supervisor/consultant will advise return to ordinary healthy boundaries.

Dozens of Israeli children develop malignant tumors from sperm donor - The Jerusalem Post

Serious disappointment when the client cancels a session.

Session-expressed curiosities about client details not relevant to the therapy.

These items can happen fleetingly, briefly, in any therapy, but if they’re frequent, it’s definitely time for the therapist to get some good, solid supervision/consultation.

What's the difference between “ce”, “ça”, and “cela”, and when do I use each (French)?

Obsessing about clients outside of work hours.

Struggling with fantasies of deeper connections with clients, whether sexual or parental or other intense or intimate relationships beyond psychotherapy.

Eager anticipation (or anxious anticipation) of the next session in ways that distract.

Why do flat Earthers still exist even though it is scientifically proven that the Earth is spherical?

Routinely going over the time limit with certain patients, compromising the time for the next client.

Off the top of my ancient head:

Frequent phoning or texting of clients to “check up on them and make sure they’re OK.”

The world of the Harry Potter series is usually considered bad worldbuilding. What are some examples of actually good worldbuilding in the books/movies?

Sense of competition with persons who are important in the client’s life.