Twitter hide replies will let you hide certain replies on your tweet, while also giving you the option to view hidden replies.
Jane Manchun Wong discovered that the "Hide Replies" feature is about moderating discussions on the platform. The original tweeter can choose to hide replies from their tweets. The hidden tweets can be viewed by others, by clicking on the option "View Hidden Tweets".
The Twitter hide replies feature is kind of similar to "Sensitive Content" of Instagram, where a user can mark certain content as sensitive, and a viewer can view that content by permitting the platform.
Also Read: Twitter lists out actions undertaken to protect integrity of election conversations
Michelle Yasmeen Haq, Senior PM, Twitter provided more context on the feature. According to her, the conversations and discussions on Twitter are between four groups: authors, repliers, the audience, and the platform and it's important to maintain a balance without overcorrecting.
Michelle stated, "We think the transparency of the hidden replies would allow the community to notice and call out situations where people use the feature to hide content they disagree with. We think this can balance the product experience between the original Tweeter and the audience".
Update(17th April 2019): Twitter has confirmed, the Hide Replies feature would launched in June, to give users a way to experiment with control over their converstaion.