Funny story; before there was a dedicated button, people did precisely this. You'd see tweets of the form "RT @Someone (their message)" The "adding context" bi

Funny story; before there was a dedicated button, people did precisely this. You'd see tweets of the form "RT @Someone (their message)" The "adding context" bit didn't really happen, because quoting the tweet ate your own 140 character limit, and a viral RT is always going to get more exposure than your explanatory reply.