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

Off the top of my ancient head:

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

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

What do you think is the most powerful line in the song "Non, Je Ne Regrette Rien" by Édith Piaf?

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.

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

How do I deal with autistic burnout/meltdown/shutdown when cooking?

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

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.

Obsessing about clients outside of work hours.

How do people in your country say "you're welcome" in their native language(s)? Is it a commonly known phrase or do most people just reply with "no problem"?

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

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

General Introduction to Boundaries from Panahi Counseling:

What is the rudest/meanest thing a family member has said to you?

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