The new mobile chat
The new mobile version of chat is now the default mobile version on devices that support it.
Unlike the classic (okay, ancient) version, it allows you to perform actions like editing, starring, and direct replies to particular messages.
The classic version is still available and will be used in browsers that lack support for some necessary features of the new version. Logged in users can also choose to continue using the old version on the preferences page of their user profile.
Please report bugs and other issues on Meta Stack Exchange. Thank you!