Today was the second time I came across an edit that was trying to remove/correct an OP's misconception. I'm sure this is has happened before and I'm sure it will happen again.
My opinion is that if the OP thought that MAC addresses are part of HTTP or called a key exchange protocol an encryption protocol then there must be other people thinking the same, and the correct way to handle this is with comments and answers.
Next time someone finds the question on Google and clicks on it, they'd see that they had a misconception and reading the answers would rectify the situation.
Editing out the misconception, however, teaches the OP nothing. Even worse, it makes it harder for the answerers to truly answer the question. Anything they say might sound confusing to the OP because the initial misconception hasn't been cleared.
In that particular MAC question, the misconception was becoming a major point of the answers, when it seemed like a minor point of the OP, thus confusing the issue at hand. I felt that the community was reacting to a mis-statement in the title, instead of handling the underlying question as laid out in the question's text. The intent was not to correct the OP's understanding of MAC.
I agree that questions where misconceptions are the major issue need to be handled in the answers and not by editing the question.