If you quote or paraphrase a work of literature or other in a post here, please include a precise citation that allows others to find the passage in situ. I've noticed many posts on this site that have not done that, and it's starting to annoy me.
Questions probably benefit from citations more than answer posts; if I'm going to attempt an answer, I'd like to see that quote you posted in context, and see if there's any material that's relevant to answering your question in the surrounding text. Of course, answers are also greatly improved by adding citations.
Besides, it's just nice to others if you don't force them to search (laboriously, if they don't have a digital copy of the work available) to find the thing that you have already found.
I don't think you need to quote the page number (unless there are relatively few editions, and the page numbers help greatly in finding the passage you need), or the edition (though that might be nice, in case there are many editions and/or you know that things have changed between editions). However, I think that the chapter should always be included in the post.
I do think you should cite the issue and page number if you're talking about comics. Even when there are digital editions available, apparently many common digital comic book formats don't have full text search. Including the page number ensures that someone reading your post will be able to find the quotation/panel that you've mentioned in your post. (And the issue number is obvious; it's no less valuable than a chapter number.)
Rule of thumb: include in your post whatever information allows other users to find the passage with relative ease.
In the first version of this post, I specifically excluded mention of voting, as that is always personal discretion. This seems to have confused a number of commenters and answerers, so let me clarify: I'm not advocating downvoting posts that don't include citations. Voting is always a matter of personal discretion. Users should downvote posts that they believe are low quality; missing citations can be a factor in judging quality, if voters so desire. In case you were wondering, I personally do not downvote otherwise good posts with skipped citations; I'll just leave a polite comment and leave it at that.