A few Twitter.com users this week noticed an "Open" button on tweets to show the full conversation, linked media, or retweets right inside the Timeline. It's a cleaner, simpler look for Twitter, and it also leaves the sidebar open — Twitter's been pushing the Promoted Trends and Recent Images in its sidebar of late, and now they're always visible. We're a little surprised to see significant changes on Twitter.com only three months after the two-columned "New Twitter" became the only Twitter, especially given the positive feedback the new look received. Of course, none of these new features have been formally announced, but Twitter has done this type of super limited rollout before, so we wouldn't be surprised to see these changes hit a broader audience before long.