One issue is that there are people that do monetize their youtube channel. Does that count as self-promotion if you're trying to build your youtube subscriber count? Does it matter if your youtube videos are technique based or product based? For example I find that Fireball tool's channel has become more of a self-promotion of his products recently but does have some good machining content in the mix.
I personally also think someone's ratio of video post to general discussion posts may be relevant. If someone posts an occasional video showing something, and is a regular contributor I think they should get more leeway than if 50% or more of their posts are "see my latest video".
Anyway, not my forum to decide, but I can see there being some need for clarification from the site mods.