A problem I've found is that, once you really understand how each word you speak (or write or type) can influence your audience, it can become hard to restrain yourself from purposefully manipulating people. And most people are so damn easy to manipulate.
Just rapping.
I might argue that few yet - with the knowledge to manipulate in comparison to the subsequent "ideal" set by the Dunyain - have such restraint and expertise with oratory to do so, specifically. While it may be an aspiration, not personally, for those who practice with such linguistic mechanisms in mind, a la abstract, few, if any, have cultivated such acutely focused levels of attention.
As Jorge suggested, many of the historical examples remaining are the result of collective noospheres working to hit as many of those mechanism as possible, in tandem with one another.
Duskweaver may be talk about diction, or manner of articulation - even taken to Dunyainic extremes) on the other hand but this is simply the result of biological predisposition and embodiment practice, which does not allow for any significant communicative advantages in manipulating particular behaviorial outputs (at least, until such a point that research, dissemination, and practice happens towards those ends - see, Neurolinguistic Programming, which I think disregards critical aspects of effective oratory).
Eventually, you start to feel a bit like Inrilatas: when every word, every gesture or expression, every subtlety of tone and cadence, becomes a potential tool (or even a potential weapon), how can you really be said to mean anything you say? Even if you feel like you're being honest and "speaking from the heart", how can you be sure you're not just manipulating yourself in order to more easily manipulate others? After all, the best liars and conmen are the ones who really, genuinely believe the lies they're telling while they're telling them. There is nothing so convincing as conviction.
+1 Duskweaver
It would be like Usain Bolt trying to let a young cousin beat him in a race. As far as social interaction goes, I would imagine that people fall into one of two categories: either they are attempting to "speak from the heart" when, in fact, no such objective personal state exists, or they forgo trying to resonate with their "true self" (which doesn't exist) and act/speak how they think they should in order to accomplish a certain goal (manipulation, simple acceptance, etc.)
Might I offer a third category by which a person engages in a relentless disassembling of their own linguistic utterances for purposes of self-understanding?
For instance, behavioral psychology might hazard a further statement, that certain constitutive criteria, either endogenously (within the body-mind) or endogenous (within the environment) stimuli are biologically inherent or conditioned resulting in specific sonically coded, information packets, depending on the sounds one makes. In which case, Kellhus or the World, you do not own your communicative expulsions, regardless, and all linguistic practice may be inherently inseparable from manipulation, as far as communication attempts to always leverage some environment reaction.
