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

Serious disappointment when the client cancels a session.

Off the top of my ancient head:

General Introduction to Boundaries from Panahi Counseling:

I think that being gay is wrong, but I treat gay people respectfully like any other person. Is it homophobic? Or offensive in any kind of way? Aren’t disagreement and discrimination two different things?

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

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

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

Why won't my mom let me come home if I'm homeless?

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

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

Obsessing about clients outside of work hours.

Is Veuve Clicquot Brut a good champagne?

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.

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

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

This moon in the solar system continues to surprise scientists with the discovery of alternating water forms on its surface. - Farmingdale Observer

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