These issues are not as simple as you think.  But anyway, clearing the shell in #6143.

Shell is a modified editor.  Currently, the arrows move the cursor around just as in the editor.  For multiline statements, this is essential, and even for single-line statements, not as useless as some claim.  Single-line command consoles can get away with changing the meaning of Up and Down.  This is discussed in #2704, and what I said above is explained more in msg243140 of May 2015.

I have a question about Linux consoles.  Windows Command Prompt is strictly a command *line* console.  It sees

>>> def fib(n):
...    if n >= 2:
...        return fib(n-2) + fib(n-1)
...    else:
...        return n

as 5 commands.  Its history mechanism retrieves a line at a time.  Does a Linux console retrieve all 5 at once, as IDLE does?