It's a strange behavior, at least to me. Sometimes I see the "edit" link below a question/answer of others, usually I don't see it. So what kind of question/answer can I edit? Or it's a bug?
And sometimes I see that others can edit my question, too.
Here is a question/answers I have the right to edit: https://stackoverflow.com/questions/784461/how-do-you-clear-your-mind-after-a-day-of-coding-closed
For example, I can't see the link to edit in this question: PHP search key in array and return its value?