This site is not just another place on the internet; an explicit (SE) goal is to have a good signal-to-noise ratio. "Wall of text" questions and answers are noise — they show a lack of effort, a lack of respect for the reader, and often lack clarity of expression. "Here, you figure out what I mean."
While I occasionally assist in making such answers look like intelligible answers, that at best addresses the symptom. Such behavior, doing the work for the badly presented question or answer, sends the signal that making noise is acceptable since "someone else will take care of it."
This answer in its original, unexpurgated form is what drew my attention to this issue, but it's not the first.
How does this site make it clear and unambiguous that wall-of-text is not an appropriate format for presenting questions and answers here? I had in mind a meta or FAQ that we can link to in comments like the How Are We Different Than Other Sites meta.