Filling in gaps in lecturer's instruction
Remember that this is a postgraduate degree. The lecturers aren't there to serve it to you on a plate. You are a grown-up now, you're doing a higher degree. That means you should be expecting to do most of the work for yourselves, and to think for yourselves.

As there's an online course discussion forum, that seems like the perfect place to work with other students to fill out the richer tapestry of knowledge that the lecture was on; post something there about useful key terms to find relevant literature, along the lines of the following:


  I found these papers (give linked DOI or other robust form of link) on the Dunning-Kruger effect. My search terms to find them were: "cognitive bias", "self-assessment". I looked in these databases / used these search engines.


Fill in gaps. Don't try to look smarter than the lecturer. It's not at all likeable, and you're only risking looking foolish later.

So if the lecturer talked about solving a particular problem by applying X, and you've found examples of people doing it by applying Y, say just that. If you can link to a paper that compares X and Y, even better.

Please do bear in mind that the presence or absence of expressions of uncertainty ("I think that ...", "I don't believe that") do indeed often mark the difference between expertise and weak knowledge. But in the opposite way round to the direction you might think. Presence of expressions of uncertainty often indicate deeper knowledge and expertise. The person who says to fellow academics "I am sure that ...", "I know for a fact that ...", "No one in the world tries to tackle it this way ..." is often, in doing so, flagging up their own lack of expertise.

And yes, all lecturers are mortal, and not every statement they make will be accurate. And that's alright. A degree is an exercise in learning to think, at least as much as in acquiring knowledge. Develop your critical thinking on all materials provided to you, whether they are written, spoken or however they're delivered.