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

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

Serious disappointment when the client cancels a session.

Off the top of my ancient head:

An AIDS orphan, a pastor and his frantic search for the meds that keep her alive - NPR

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.

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

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

If you caught a shoplifter at your yard sale, how would you handle it?

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

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

Obsessing about clients outside of work hours.

I see ugly guys dating gorgeous, "hot" women all the time. I, too, am not very attractive but I'm not doing well with the ladies. What's their secret?

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

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

General Introduction to Boundaries from Panahi Counseling:

Is it true that all men want a woman who looks like an Instagram “model”?

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