Is it healthy to use humiliation as a punishment? I mean, it's fun during scenes. You know it's just play & you can always use your safe word if your Dominant hits you where it hurts. During punishments, you know your Dominant isn't pleased with you, which is painful enough alone. That's why you're being punished: You did something wrong & he's not pleased with you. And many Doms don't allow you to use safe words during punishments. Mine doesn't, for example. So how would they know when the humiliation is damaging you? Is it possible to use humiliation as a punishment without damaging a sub's self-esteem or is it best reserved strictly for play alone & nothing more?
Humiliation is a delicate game. It can cause harm if done incorrectly. Heated emotions tend to come up just before and during a punishment. While I advocate that no one serve a punishment while angry - it is likely to still think about the infraction in the process of doling out punishment. This increase in emotion can cause the Dominant to stop watching their submissives reactions and they could go too far in humiliation. It happens in play and it happens in punishment. It's a hard thing to gauge when you've gone too far if the submissive can't safeword - but that doesn't mean you shouldn't speak up as soon as possible. I doubt that they intend to really cause you harm and would need to just have a nudge that you realize you are in the wrong but you are beginning to feel "x, y, and z" about what they are saying/doing.
I am guessing that you are specifically asking about verbal humiliation. Things like being called a worthless sack of donkey poo or something. It can get out of hand if they hit a really sensitive area for you. Talking about it afterward can help the Dominant understand where they took you and why it wouldn't be a good thing to use in future punishment. Good Dominants do not want to damage their property.
But when done effectively it can serve a purpose in punishment also.
Say that you are a submissive who as a rule has to ask permission to use the restroom. You've made a mistake and are to be punished. A Dominant could say that your punishment is that you can not ask for bathroom privileges until after you have peed yourself. Thus a humiliating punishment is born. Some submissives may wait until they just can't hold it in, and am embarrassed by that, while still others just make themselves do it as soon as possible. Either way, it's still embarrassing to pee yourself as an adult and the lesson has been learned.
I hope this answers some of your questions.