In a blog post Twitter’s Director of Product Management Suzanne Xie said, “Sometimes people are more comfortable talking about what's happening when they can choose who can reply.” If people are worried about being bombarded with unwanted replies or want to limit a conversation to specific people, this is the way to do it.
Even if you limit replies to a tweet, anyone can still view, retweet, retweet with comment, share, and like the tweet.
Xie said that: “Since we started testing this in May, people have used it to host interviews and panels, share what’s on their mind, and make announcements. We’ve learned a lot from usage, feedback interviews, and surveys. These settings help some people feel safer and could lead to more meaningful conversations, while still allowing people to see different points of view.”
She also pointed out some interesting findings, such as 60% of those who used the feature when it was in testing didn’t mute or block anyone as they had more control over blocking out unwanted Twitter noise.