Twitter has recently announced it is now live testing the new controls over who can reply to users’ tweets. As of now, a limited group of people will have access to its audience control feature for tweets – which will allow them to restrict who can reply.
As mentioned by the company, “Before you Tweet, you’ll be able to choose who can reply with three options: ‘Everyone’ (standard Twitter, and the default setting), ‘Only people you follow’, or ‘Only people you mention’.”
Hence, the reply icon will be inactive for the public, to indicate that it can’t be replied to. The people who can’t reply to those tweets can view, like, and retweet with a comment like usual.