It used to be the case a long time ago that when you type in a URL into a Gmail compose window, and after typing in the last character (or immediately after pasting it in from the clipboard), and typing space, the URL automatically becomes a link.
Then at some point it, they changed the behavior such that typing a space character no longer turns it into a link. I have to select the whole URL with the mouse and type CTRL-k to turn it into a link.
This is the behavior in Google Documents and I would like to re-enable it for Gmail.