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

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

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

Obsessing about clients outside of work hours.

Why can't my adopted sister accept she is not part of my family because she isn't related? Why can't she stop calling my parents mum and dad?

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.

General Introduction to Boundaries from Panahi Counseling:

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

Why is Eric Clapton so roundly disliked among guitarists?

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

Serious disappointment when the client cancels a session.

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

Can you describe what it's like to live in a town known for Harley Davidson motorcycles?

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

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

Off the top of my ancient head:

Why one mom is trying to delay her daughter’s first period — as experts warn of the risks of early puberty - New York Post

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