Very occasionally, I have noticed that wily gets into a state where it will
duplicate single characters in a file, during editing. I have
just seen it do it: I could press return to replace a linefeed and tab
with a linefeed and plus tab (autoindentation on) and it duplicates a character
later in the line. This could be 'Undo'ne and repeated.
I have no idea what causes it to get into this state, but once it's in it, it happens quite frequently and a file ends up with scattered duplicate characters.