During a discussion I was responded to me with:
There is NO such thing as “leaderless” organisation amongst humans - period.
and I don't know what to make of it. I don't have enough first-hand experience with anarchist organizations to refute it but I have read and watched enough anarchist media to doubt this claim.
(Edit: probably should have mentioned: This was told to me by another anarchist who I've seen in this com. So I don't think this was due to ignorance.)
My main inspiration for my own beliefs comes quite a lot from the youtuber andrewism. Because the way he describes anarchism speaks to me. It's hopeful and constructive focusing on the things we can build instead of the things we must defeat, something that very much resonates with a naive pacifist like me.
He has made a video on the topic: https://www.youtube.com/watch?v=AYVWbj8naBM.
And he does a good job of listing all of the different ways of leadership, until ending with the idea that leadership could be used as a way to start enforcing authority, and that constant vigilance is needed to oppose it. He therefor argues to view leadership not as a position, but as a practice that is shared across everyone.
There is also this comment under the video that I think is relevant:
I think that calling it a "guide" instead of a "leader" would properly convey the idea. Why is a guide a guide? Because of their local (or niche) knowledge, e.g. somebody who guides you around a museum. There is no inherent authority caught in the word, as you are simply choosing to listen to them concerning a specific context.
There is also this text: https://theanarchistlibrary.org/library/anonymous-all-cocoons-are-temporary
Which I remember really resonating with me but I can't remember most of the specifics so I guess I'll need to re-read it at some point.
It is possible to run truly always-leaderless collective. The problem is, it is fundamentally the least anarchic, humane, and free solution there could be.
As problem stated, there is always a case for organizational violence - at very least, the membership rules that require value coercion or expulsion in case of values misalignment, but usually much more - without this violence, it's not really an organization, but (of course temporarily) aligned group of people - the best social state, that actively resists scaling, translation, and its own survival over time - which is not bad at all, this is true pure anarchic state of freedom, but certainly not an organization. Yes, TAZs in popular reading are built around some internal violence too.
Whenever this violence is required, it comes to whatever is the source of violent decision making. If there is a leader, we could at least be certain that the decision was made by a human being (or, if we end up having aliens or proper lucid AI, which, IMO, should have same rights as we all), accountable, empathetic, thinking freely. In truly leaderless collective, decision making inevitably falls into hands of algorithm, wherever collective members are not perfectly aligned (and they are not, for call for abovementioned violence requires that alignment is violated) - then decision is made blindly, by unaccountable abstract entity that has really no empathy or other humane features.
In other wording, the violent decision ends up pretty much almost always wrong, which brings us to Condrocet paradox where large number of decision makers are worse than singular leader. This is even more true in hard, dynamic situations, like activism or first-response management, as other commenters pointed out, and there are often no "right" decisions.
Thus, even disregarding dynamics of all communities of interest to be discussed here (I've seen successful examples of leaderless trade teams, or tech cooperatives tightly bound into capitalist fabric - in other words, systems, where total replacement of humans by machines would not be noticed at best and would be beneficial for the systems really), an organization without a leader is dead or saint relying on pure flow of miracles.
This does not mean that anarchy is impossible, of course - even random rotation of leadership through collective members makes the system almost pure anarchic setup.