Televangelist Robert Tilton manipulated people in an anti-social way - so don't do that. But Bernie Sanders manipulated millions to become politically and socially engaged.
I think for me, the gauge is: if the other person found out I was actively using tactics on them, would they be angry, or accepting and curious? Tact has a lot to do with it, and who you are otherwise.
It's just like anything else; some people can tackle new subjects completely on their own, but almost everybody benefits from good advice. Why should advice on getting along well with others be withheld?
I don't think anybody intends to be a bore or a jerk, yet obviously some people are. It affects their lives profoundly, and they may lead lonely lives. Withholding advice on how they could be more likable, if they're so inclined, seems a little cruel. If you'd use the same advice to manipulate people, that's on you.
On the other hand, prompting people to talk about themselves, assuming you actually listen, doesn't seem terrible to me. I suppose there's a line between purposefully trying to make an impression and hacking people.
This sounds a bit more OK to me, but still the notion of manipulating others does get under my skin.
If you go into a conversation and the result is that the other person thinks you are uninteresting and they don't have anything to say, it is negative for everyone involved. Productive conversations are usually productive for both people, it's not likely that you are somehow sapping away something that belonged to another person, rather that you are turning time spent by both parties into something of value to both of you instead of wasting it.
I'm not sure that's true, but it does occur pretty often in all sorts of situations.
I'd bet if you took that view into many of those types of conversations, you wouldn't feel bad
(Finally, please note that I am explicitly excluding anything immoral. )
Stop trying to impress people or "win" the conversation. It's really much simpler than that. Just listen intently and make people feel good about themselves.