Welcome to Gaia! ::

I think in general scanning thoughts of others is okay, and in general projecting thoughts is not. Scanning thoughts in general is done more as a protective measure than anything else, if however one uses what they find there to manipulate or blackmail the other person that would be wrong. Likewise projecting thoughts into someone's unsuspecting mind would be a manipulative act, however if you were doing so in an attempt to save them from hurting themselves or someone else, as in a suicidal person or someone who is distracted while driving and you send a mental message to look up or watch out, than that would be an acceptable use.
I do believe humans deserve privacy, with my empathy I pick up on things inadvertently sometimes be it a thought or an emotion of just the gist of something wrong. Unless it strikes me as something life threateningly serious I simply pretend I didn't sense it at all. Your mind is one place you should always feel safe and free.
I think psychic influence is different from social influence in that with most people are aware of social influence and the signs of it, there is always some kind of trail, whereas with psychic influence most people are unaware of what the signs of it are, how to detect it, resist it should that be their will, thereby giving the psychic doing the influencing an unfair advantage.
Reading this is a little different than psychic suggestion because most people are aware of how to pick up on biased or leading wording in written material, therefore they have the ability to resist it, and as it is something we can look at objectively outside the realm of our own mind and own thoughts is makes it easier to separate from what is and what is not our own thinking.
I have no idea if that last bit made the slightest bit of sense, I hope so. Wonderful, thoughtful questions as always Viscerim.