It would be nice if the @username autocomplete idea for comments could be extended to answer posts. Although, what I'd really like to see is a faster way to reference other people's answers to a given question, within your own answer. Say user 'foo' already posted an answer. I would like to provide a link/credit to foo's answer within my own answer. As it is right now, the only way (that I know of) to do this is by copying the link to their answer and creating a link within my answer. It would be a small time-saver if the @username notation could be used to do this instead, such that @foo would be automatically expanded to a link to foo's first answer in the current question.