I've occasionally opened a post, seen a couple long, seemingly-sourced answers, and read them. Then I come back to the post the next day, and one of the answers I read is gone.
Am I alone in wondering what it is I learned that is incorrect? I read the post, internalized the details, but clearly something about it merited it's deletion.
It bothers me on some level to know that I've read something not-quite-correct, especially since there are numerous facts and figures in a typical answer, and maybe some of that information is still correct.
An answer can be well-written, logical, cite several sources, and still be incorrect. Often moderators leave a comment telling the redditor why their post was removed, although on very busy threads it isn't always possible to do that. Moderators also sometimes work with the redditor about how to improve their answer.
One of the major issues is often that the redditor simply doesn't have enough background in the subject to answer follow-up questions, doesn't provide sources on request, or demonstrates some fundamental misunderstanding which calls the quality of their answer into question - such as relying on older sources, pop history, or largely discounted theories, which can be hard to spot, especially if you aren't already an expert on the material.