What are the cases when it is considered appropriate to edit someone else's question or answer?
Specifically, I think there's a significant safety risk in the question about scallop preparation. I provided details in the comments and added a warning to the answer. Is that appropriate? (based on answers so far, I've rolled back my edit. See revision history for what I had written)
In addition to that specific question, I'm interested in the more general case of when it's ok / encouraged to edit an answer.