I'm afraid this will not be a direct answer, but first a series of questions to help you think through what you are asking.
(1) Did the insight come from the lecturer or someone/something the lecturer taught about? In other words, was this insight the creation of the person teaching the course? Or did (s)he quote someone else/some other study?
(2) If it wasn't an online course, and you physically attended the course, would you cite something you learnt there?
(3) Is this insight peer-reviewed, or does it have any other basis for it's validity?
(4) Can another researcher easily access this insight using your reference? (Easy here is referring to effort required, not cost).
(5) Are you confident that you are allowed to reveal this insight in your work, i.e. it does not run afoul of the license used by the course/course aggregator?
If the answers to most of these are 'no', you probably shouldn't add it as a formal reference. Remember, teaching aids are teaching aids, you don't see them cited unless they are published textbooks or reports. If it's an oral insight, it's all the more difficult to fix accountability in case of misuse. If it's not reviewed or published, one may rightly question why you believe it to be true. If it is sourced from other material, you should cite the original material, not the lecture. A reference should be verifiable by a researcher. If I want to access this insight, I wouldn't want to have to sit through a course for that. The licensing issue speaks for itself.
This is not to say that only peer-reviewed literature should be cited; I asked a related question about non-academic documents and received helpful answers here on ASE, you may like to take a look.