Visit gmail using Safari for Windows, and start composing a mail. Compose a sentence such that the sentence ends just at the right edge of the composition area (but not so close that it will wrap the last word when you hit a space), then type two spaces and start a new sentence. Notice that the line wrap is inserted between the two spaces, causing the subsequent sentence to be "indented" one space on the next line. In other browsers, and in Safari 2 on the Mac, the wrap happens after the double spaces. (I have not tested trunk on Mac.)
Also happens in Mac Safari w/ WebKit r25796, so this is a regression for Safari 3. (I don't know how I'm supposed to mark that.)
Confirmed as a regression with r27834.
I can no longer repro this.