Its right there in the privacy policy: https://twitter.com/en/privacy https://twitter.com/en/privacy > When you use features like Direct Messages to communicat

Its right there in the privacy policy: https://twitter.com/en/privacy https://twitter.com/en/privacy > When you use features like Direct Messages to communicate, remember that recipients have their own copy of your communications on Twitter - even if you delete your copy of those messages from your account - which they may duplicate, store, or re-share.