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

General Introduction to Boundaries from Panahi Counseling:

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.

Why can't flat-Earthers create an agency like NASA to explore Earth to prove it is flat? What's preventing them from doing so?

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.

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

Yang Hansen Already Winning Over Fans at Introductory Press Conference - Blazer's Edge

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

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

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

Many forget the damage done by diseases like whooping cough, measles and rubella. Not these families - AP News

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

Off the top of my ancient head:

Serious disappointment when the client cancels a session.

Is it okay for a wife who comes home from a date to tell her husband what she did?

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