> When I worked in networking, and later web dev work I found Reddit to be a TERRIBLE place for Q & A type situations.

Training in this sense is about how people use language not what is the right answer. Among other sources - the exact thing you describe is a contributor to some of the things within the (in my opinion misnamed) internal taxonomy of 'hallucinations'.

Right or wrong - reddit is human beings using (mostly english) language to speak to each other, and so if you want to train an ML model to do that - its a great source.