In your setup, is the red color the modified color, and the darker one the inserted line color? The easiest way to get to those color settings is Document -> C++ Options -> View, and clink on the hyperlink next to the "Modified lines" option.
So far, I don't see this. The comment wrap does put a space on the end of the foo when I hit enter, but the space is removed when I save as long as I have the strip trailing spaces options set like yours.