[throwaway2037]

I think that you raise some excellent points here. I want to dive deeper into what is meant by domain knowledge -- as a I see it. This phrase comes to mind: "Those who know, do. Those that understand, teach." (Google search tells me that it is frequently misattributed to Aristotle.) People who cannot clearly articulate rules for their domain only "do". However, those that can clearly articulate will "teach". Thus, I would say true domain knowledge is the ability to teach that domain to others.

[layer8]

I largely agree, but want to note that there’s the counterpoint “Those who can, do; those who can’t, teach” (from George Bernard Shaw’s 1903 play Man and Superman), which also has some nugget of truth in it.

[rightbyte]

Case on point is Youtube where a lot of almost good amateurs give a lot of advice on niche channels on things they hardly master.