Twitter announced that it is experimenting with the new "unmentioning" feature. It is designed to let users remove themselves from unwanted conversations.

The option to "leave this conversation" will appear on the menu that can be found in the corner of a tweet on Twitter's web version. Once you click on this option, you will see another menu with a detailed explanation of what will happen when you leave a conversation. Namely, your username will be untagged from the original tweet and all the replies, future mentions will be stopped, and you won't receive any further notifications.

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The company first announced the news on its official Twitter account on April 1, but the public took it as a joke at the time. However, Twitter confirmed the new feature later on April 6, so this is surely not a joke.
Recorded News — Tech NewsBradley Rhodes

The new tool will help avoid "unwanted attention" to users, as such cases often lead to bullying on social networks. Or users will simply have an ability to leave the conversations they are no longer interested in or do not want to be a part of.

The new feature is currently limited to some users and is only available on the web version of the social media platform.