The benefits are manifold. Not only can you read multiple messages, you get to see them without extra lists and gimmicks to their left and right, too. Not only can you continue reading even after you have technically deleted the email, that works with archiving, too.
Open an Email in Its Own Window in Gmail
To open a conversation in a separate browser window with Gmail:
- Hold down Shift while clicking the message.
With the keyboard alone:
- Position Gmail's message cursor in front of the desired message using the j and k keys.
- Press Shift-O.
With the mouse alone:
- Click the desired message in the message list.
- Now click New window.