Prevent this user from editing his own talk page while blocked checkbox should be disabled and ignored unless a namespace restriction for User_talk: namespace is in place. In this scenario the value of the checkbox should be honored.

If wgBlockAllowsUTEdit is set to false, the user should always be able allowed to edit their own talk page unless a restriction for the User_talk: namespace is in place.

Sitewide blocks behavior should not change and should always honor the checkbox.

For more details: T210475: User should not be allowed to edit user talk page if checkbox is enabled (partial blocks)