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.

Serious disappointment when the client cancels a session.

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

Gun owners, imagine if an attacker comes to your home and takes your gun to use against you before you had the chance to pick it up. Would you regret owning a gun?

Off the top of my ancient head:

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.

Why didn't my ex fight for our relationship? He gave up so easily.

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.

General Introduction to Boundaries from Panahi Counseling:

How do I become a Buddhist, and can someone explain Buddhism to me?

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

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

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 am I so afraid that gun owners have set traps to kill me outside my house or my car?

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