The dialectic between teacher and learner is one of great importance but is often misunderstood or, perhaps in more weighted terms, is not brought to its full potential by the teachers.
This permeates in the marxist environment, which is the only one I'm concerned with currently, where teachers do not realize their role and full capabilities as such. It remains by and large -- in my experience only -- as not a dialectic, but a unidirectional conveyance.
The teacher speaks, and the learner listens. This is the metaphysical model.
But are we not all being taught, and thus learning, at any time? From discussions I've had where I started in this metaphysical "authority" role of the teacher (a role most people, me included, subordinate themselves to rather easily as what they think a learner should be) and ended up learning more than I taught.
I may know dialectics well. But I may not know economics well. A learner is a fluid thing, it goes through stages back and forth. I teach dialectics to someone, and I learn economics from them. By asking their questions, they help me refine my understanding -- and capabilities to teach -- of dialectics further.
The teacher should explain, promote, make considerations. The learner should retain, evaluate and analyze.
This requires for the learner to understand that their role is not simply to nod along and retain everything from the authority, and for the teacher to be open to changing their mind and methods.
The dialectic (contradiction) is resolved when the session gives birth to a new third thing, in this case similarly to the "original" Ancient Greek dialectic, and both parties come out with a third new idea that did not exist previously. The learner has learned and taught, and the teacher has taught and learned in a way they both further their understanding of the topic.
It can then repeat with the learner being able to become a teacher (in any capacity) and the teacher having refined what they will say (and how) to the next learner.
I see the complete opposite too often; marxists that would rather confirm their biases, eschewing their own capabilities as teachers (and learners -- many think of themselves too highly to still be "learners") and completely smothering any potential their interactions may have had as a teaching opportunity, at least dialectically.
You see this most often on social media, where the order of the day is to make cheap jokes, quick "stream of consciousness" quips, and confirming one's own already formed beliefs.
In this role, they are being metaphysical (or at the very least undialectic). It's not bad for the sake of it and me being able to use the jargon; it's a malformed process because dialectic cannot take place, and cannot make things advance. Thus they remain stuck where they were exactly before: further confirming their belief that their tendency/ideas are the best, and working not to advance that tendency or idea, but to disprove that any other is good.
I can only speak to the western english-speaking parts of the internet, but from my experience with them, there is a big problem of arrogance and ego, and I don't exclude myself from being caught up in it at times; I have tried to consciously unlearn those tendencies, but I suspect it's made more difficult to do so living in the US, with all its caste and competition.
I find that whether it's social media now, or smaller internet forums a bit further back, it's common for people to make confident assertions on things they know nothing about; invent entire explanations out of thin air rather than investigate their source; and generally derive pleasure and self-esteem from being perceived as the "smartest in the room, the most smooth and well put together." One way I think I could misstep here is in looking at this and doing the liberal moralizing thing of saying, "I don't want to be consumed by such base desires, so I will not try to present my ideas in a way that is compelling and will instead just sort of throw them out there and hope people listen." But then I am abandoning effective rhetoric as a tactic, for fear of it being "corrupting."
It may be that there is a time and place for quips in order to puncture any notions of the other person having something valid to listen to. But if it is not done tactfully and just done sloppily in order to indulge in arrogance and ego, then I would agree we aren't really gaining any ground there.
Asking what it is exactly that we are trying to "advance" in context may be helpful. We can know, vaguely, for example that we're trying to advance "communism", but there are also fascists who pose themselves as communists, so we can't depend on that being enough to clarify in vague language. We can know that we're trying to advance anti-imperialism, but being anti-imperialist does not automatically make one's cause communist. We can know that we're trying to advance working class interests, but some working class elements, such as in the US, are imperialist or racist still and need to unlearn that if they are to be part of the liberation of the international working class.
This can slow things down and on some platforms, in some contexts, it may be more important to say anything rather than getting too deep into how to say it and what the aim is. But some of this reflection can be done outside of heated exchanges, even such as right now, with others who are of similar views. So thanks for bringing this up.