You can do this in the standard reply box without using rich text. The part that says target=”_blank” is what makes the link open in a new window.
If you want to use the rich text editor instead:
1) type the link title first (e.g., ‘Jim Klinge’s listing’)
2) select that text with your mouse (it will highlight)
3) click the link button (near the formatting icons, looks like a chain)
4) A popup will be displayed where you can enter the actual URL and select the option to open the link in a new window (or not). Ignore the “Title” field in that popup as it won’t actually help you.