Hi,
the console prompt is "?" or actually "? " with a blank. Using
backspace 
to delete that first blank is impossible for a reason. However, I saw 
that it is possible to position the cursor (caret) behind the "?" with 
the mouse. Example input then: "?=5", which provokes a broken console 
error. This was just an accident by clicking the mouse somewhere in the 
console, but I wonder if it's possible/worthwhile preventing.
cheers
sven