Stack Exchange has a lot of general guidance on how to use the site, including how to ask and answer questions. One of those concerns the topic of self-answering questions (or more specifically, posting questions to which you already know the answer for). However, many communities across the SE network approach those matters differently, and especially given that a lot of users around here are new to the whole SE business, I think we should figure out how we feel about this policy and how we wish to deal with it.
Now, there are many different circumstances in which one may want to self-answer. The issue was brought up by Nike Dattani under this post of mine, which I posted a self-answer to, with the intent being that this is a "big list" kind of question, and my answer is just one of many examples. More "classical" kinds of self-answers are ones meant to document existing knowledge. And then of course there are cases where the person asking eventually figures out the answer after posting.
I am going to post these three types of scenarios as separate answers, so we can use the upvotes/downvotes to express our opinions (and give comments under individual answers to discuss those scenarios). Feel free to explain other situations where this question might arise in answers so those can be discussed too.