Win7x64 - brief keymode
In a C++ file I saw the following:
// AA
// BB[cursor here at end of line]
// CC
Now hit delete and the CC moves up with the "//" removed (cool) and one space to the right of the cursor (because there's a space between "//" and the comments)
// AA
// BB[cursor] CC
Now hit enter again and CC will go to the newline with "//" prepended but with AN ADDITIONAL space added in:
// AA
// BB[cursor]
// CC
Keep tapping delete/return and spaces will keep getting added, causing CC to be expanded out.