I'm generally against covert hypnosis since it is usually unethical, risky, and not effective.
It's not always necessary to do formal "hypnosis" - conversational hypnosis is great. It's the "covert" part that I'm against. I'm against hiding things. I'm against there being anything to hide. I don't necessarily call attention to labeling the situation as "hypnosis" when I do conversational hypnosis, but that is because it's not helpful and there's nothing to interest them there - and not because there's important information that I'm hiding from them.
Covert techniques, like embedded commands, can involve different levels of deception.
For example, when someone says "You totally shouldn't... buy my product", they are pretty clearly pretending that they are intending one thing, but really intending another. "I understand if you can't...make an exception now" is a little better, since you aren't actively pretending you're going for the opposite.
But even if you were to say "you should.... JOIN THIS GROUP", it's not necessarily a good thing. It's sorta open that he wants you to join the group, yet you know he's still cackling inside saying "I bypassed the conscious critical faculty with my embedded command!!! Muahahaha!" Even though it is clear that his intention was to have me join, I still don't trust anyone that tries to makeme feel a certain way by skipping past my filters entirely. I'd much rather them convince me to consider it/delay filtering until I have all the information that I need to judge it, or have them selectively disable bad filtering.
It's funny to see people like Igor Ledechowski teaching people how to do "conversational hypnosis" as covert hypnosis. He goes on about "H+" and about how you should only manipulate people for their own good (not quite his wording), but then his advertisement looks like this: http://conversational-hypnosis.com/
It's like he thinks "Well, my product will tell them to only use the techniques for good, so everyone will benefit! And it's okay if I use the dark arts that tempt them to fulfill their dark desire for power - because in the end, my intentions are good and I'm going to
tell hypnotically "influence" them to only use it for the greater good!". Terrible epistemic hygiene there. (To be fair, that's not the words he says and this is a bit of a caricature, but I the implicit reasoning does look a bit like this)
I really do think he believes in his H+ thing and that he is not out to be an evil guy, but I don't think he's given much thought to what it takes to be "good". There's this whole thing about tricking people to make them feel good and believe in themselves and think their problems are gone - without respect for their potentially valid reasoning for why their problem can't be wishful-thinking-ed away. A whole lot of good can be done by helping people feel good and have positive expectations, so I can see why they'd do it... Yet sometimes there's a real problem that needs to be dealt with too. He even talks about being genuine... and sometimes he seems it... yet it sometimes looks really goofy and not genuine to me. <shrug>
Okay, but besides ethics...
Covert hypnosis is also risky. The thing is - if the "victim" is ever like "ummm... dude, I'm onto you", it's kinda game over. No more rapport. I like to take approaches where if anyone "calls me out" on what I'm doing, the response is either "Um... yeah, I told you that" or "Umm... duh. That's not hidden, and here are three reasons why it's legit" - and then I give three very good reasons. Approaches where I'm not trying to hide anything because I have nothing to hide. For example, with this post, I never explicitly said "I will now try to help you see why I am against covert hypnosis!" but you can't really call me out on it - it's right there for you to notice if you care to.
So if I want people to join my group, I'll say "you should join my group". "OMG! you're trying to get me to join your group!" "Umm... yes. That's what I mean when I say 'you should join my group'". I might even emphasize it a little bit - "You should join my group". "OMG! You're trying to get me to join your group!" "Umm... yes. That's what I mean when I say 'you should join my group'" "But you emphasized part of it!" "Yeah... because it deserved emphasis. I want it to be very salient. Emphasis is how you say this is important, and I emphasized it because it's important" - not because I think it's a "subconscious embedded command that you cannot resist".
On top of the ethical issue and the risk of getting caught, I just don't think covert hypnosis is all that effective. If you can only give single stage embedded commands that aren't very salient, then it's gonna be tough to get anywhere. Going multiple stage and keeping the secret is a nightmare. It's so much easier to just to be up front about things. That way, you get to specifically find and deal with objections instead of weakly trying to cover them up.