That sais I think my paragraph about copying others idea came out wrong. When I'm with people, learning by osmosis often lead to superficial repetitions of some of their findings, something that is not deep learning. I like to reach the enlightening phase, ability to find solutions from blank slate, hence being alone helps avoiding this to an extent.
I think we are on the same page about your last paragraph. You are right, you face a problem of a same kind that I wrote about when learning in a group. Someone seems to know the material well, they are confident and maybe even charismatic. They go through their solution and everyone just nods and agrees.
The trick is to get everyone tell their solution (maybe not for the same problem) and have an atmosphere where people feel comfortable correcting and getting corrected. That is a key responsibility of a small group teacher.
The "peril" in self-study is a bit different. You may find your enlightenment but how do you know that your mental model is correct?
I work as an assistant teacher every now and then and it is mostly small group teaching and going over the homework exercises. What I have seen is that the first couple of sessions are totally worthless subject wise. But they are extremely critical. During those sessions the students learn to know each other and me. When everyone is comfortable attending the sessions can the actually learning begin.
From this perspective I think MOOCs would need the following. Firstly, you need to create small enough groups of people that are comfortable discussing the subject with each other. Encouraging local study groups is a one way of doing this. The other thing is to encourage discussion through anonymity with forums or IRC. And you need to acknowledge that you don't reach all of your students with these methods and not rely on them too much.
> I personally like to learn in isolation, I have a tendency to quickly ~plagiarize ideas of others thinking I understand, so learning alone in my room is better.
There's nothing wrong with self-study per se, but it has a one great flaw. It is easy do the kind of plagiarization I think you are talking about without knowing. This can be remedied by getting feedback from an instructor, or going through the material with someone else and then cross checking how you understood the ideas.