I have several comments on what is helpful from my perspective.
There is no standard reader. Try to provide an answer that will be intelligible to the less experienced while still helpful to the more experienced.
Understand that a MWE is not always easy: sometime removing "extraneous" code changes the behavior that you're trying to diagnose. It's bad enough for someone with decades of software experience; for a complete noobie it can be ghastly.
Don't just edit the code; explain what you changed and why.
If you give a man a fish you feed him for a day; if you teach him how to fish you feed him for life. Try to explain how to diagnose similar problems in the future.
When your answer refers to arcane or fragile concepts, give the user enough information to understand what you're talking about and to understand potential risks.
If you close it as a duplicate, provide a link to the original question. No, an obvious search won't always find it.
If your answer is RYFM, give the user a link to TFM.Either way, keep in mind that the user may have already RTFM and the information wasn't there, or wasn't there in an obvious location.
If you downmark a question or answer, explain why.