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

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

Obsessing about clients outside of work hours.

General Introduction to Boundaries from Panahi Counseling:

Do you have any attributes quirks sensitivities abilities etc that you've come to learn most people don't experience? E.g. dream with subtext or experience de ja vu regularly or know you experience life very differently from those around you etc?

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

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

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

Why do I get spun and then want big fat cocks to suck?

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

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

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

PCIe 7.0 is coming, but not soon, and not for you - The Verge

Serious disappointment when the client cancels a session.

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

Off the top of my ancient head:

I caught my neighbor leaving his 12-year-old son home alone and he has not come back in 6 hours. Should I call CPS?

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.