Mark Zuckerberg, take note: Twitter on Monday quietly introduced a high-visibility change in design and functionality, and no one's crying or threatening to leave the service. "Today's update better reflects how folks are using Twitter now," writes founder Biz Stone in his blog.

The change turns "Replies" on the service into "Mentions," and groups them under a tab on the left labeled with the familiar @username syntax -- for instance, for the Betanews Twitter account, Mentions displays as @BetaNews. And where previously the Replies tab showed only those tweets that began with the flag, Mentions shows every instance in any message. (In other words, it now sees "La la la @BetaNews" as well as "@BetaNews la la la.") The adjustment will help Twitter users to keep track of any conversation in which they're flagged. And as with the original @username reply flag, the new usage was developed and perpetrated by the users, rather than dictated by a design team.