There have been a few times I've seen a fantastic answer here on drupal.stackexchange and thought the inclusion of a graphic (an example or reference) would make for a much more readable answer.
I feel that creating a new answer for the sake of showing a graphic is a bit dirty. Almost as if I would be swooping in and hijacking someone else's work.
Is it appropriate to edit another members answer to add a graphic when it makes sense or is it better to create another answer with the added works?
It depends from the answer: If the answer is detailed, and it just misses some screenshots, then I think it is fine to add them. That is equivalent to add relevant links to an answer given from somebody else, which is an allowed. The "How to edit" block shown to who doesn't have the permission to edit every post says:
If the answer is very short, such as See admin/config/people/accounts. and you can provide more details, then you could answer the question.
If the answer is detailed, and you can provide important information that has not been said from the user who wrote the detailed answer, then you can add your own answer with screenshots.
