> I expect that a lot of users use the tab key to indent in the repl
> (as well as in editors, smart enough editors can convert the tab
> presses to spaces)

The interpreter prompt is not a text editor at all. You can misuse
it as one, but that's a loss of time and energy IMO.

Really, everyone I've ever showed tab-completion to has always
been enthusiastic about it ("why isn't this enabled by default?").
None has ever raised the concern of being able to use the tab key
to indent code under the prompt.

(probably because noone is crazy enough to type long chunks of
code under the interactive prompt anyway)