Earlier quoted context omitted.
Why not add a fifth point about contribute with a better answer if you know better? It feels wrong looking down on people just trying to help.
The problem is stackoverflow seems designed to avoid "better answers". Questions are often long abandoned, and the original questioner won't come back and choose a new correct answer. On a rarely looked at question, it would take years for a correct answer to raise up the ranks. I've seen various answers which used cryptography dangerously, and asked if there was any way they could be fixed, and I just got the answer…
SO is perfectly happy to accept better answers, especially to those which have gone stale and perhaps no longer applicable.
If you are offering further information that can benefit the reader its always welcome.
Its one of the reasons a lot of the more concise answers are not always the accepted answers. Because people do ask quite often : "Okay but why did that fix it"
In-fact : Answering without giving a proper reason for the solution is frowned upon mostly.