If I’d made that a tweet a few days ago, everyone would have been able to see it if you’d got the setting turned on to see all the @replies that users send and maybe you’d see an interesting conversation unfold, even if you didn’t follow me, or @austenw.
However, as I’m sure every Twitter user has seen, some changes have been made. Changes that users were not consulted upon, or given an option to change back.
Now if I made that same tweet today, you’d only see it if you were following the person mentioned in the tweet, and then if they replied to me, and you follow them, you wouldn’t see their tweet to me either, unless you were also following me, but you wouldn’t know about me via the tweeting, because you’d be blinkered to it. Confusing? Yes, but it wasn’t before.
We've updated the Notices section of Settings to better reflect how folks are using Twitter regarding replies. Based on usage patterns and feedback, we've learned most people want to see when someone they follow replies to another person they follow—it's a good way to stay in the loop. However, receiving one-sided fragments via replies sent to folks you don't follow in your timeline is undesirable. Today's update removes this undesirable and confusing option.
That’s Twitter’s official wording on the situation. Some people have suggested that they use an option similarly to facebook’s privacy settings, where you can control how much certain users see, so if you don’t want someone to see all your @’s you could switch them off that, or if you would prefer not to see any tweets with the hashtag “#lost” in over fears of spoilers for the finalé. I’m sure Twitter will cave and revert back in a few days, but to help with that, people have made the #fixreplies hashtag, which is currently #1 trending topic on Twitter, and there’s a Get Satisfaction thread (which Twitter uses for problems and such if you didn’t know).
Another headache this is causing for users who don’t want all @ replies, is that people are retweeting their replies, so that everyone can see them (as if it’s prefaced by text then everyone sees the tweet).
Hopefully twitter fixes it promptly.