This is a very subtle (and hard to remember) difference, but the heading for an answer is bolded and slightly lighter [in colour] than the heading for a question
Question
Answer
For easier comparison, I've placed them side by side below:
(question)
(answer)
The same difference is also in your Review History tab.
Note the differences between the Google appengine Q/As. The answer heading is also slightly smaller, which doesn't seem to occur on the normal Edit Review screen.
