> Lastly, for live demos in presentations, it is desirable to have a clear screen, free of distracting artifacts.  The sidebar is such an artifact -- you would never see such a thing in a book or slide presentation.  Also, for live demos, large fonts are necessary which means that screen space is at a premium and the loss of horizontal space matters.

I am not sure I agree with the strength with which you state "you would never see such a thing in a book or slide presentation".  With Jupyter notebooks being very prevalent these days, samples very often include the non-code visual artifacts native to that format.  Arguably, the *prompts* are a distracting visual artifact; the ability to cut them out of screenshots from Jupyter notebooks thanks to the clearer separation of cells and their inputs and outputs is indeed a boon, and we could consider whether we can do something similar for IDLE.

As for lost vertical space, that is indeed at a premium for books and presentations.  However, ipython significantly increases the vertical spacing to the left of code inputs and non-stdout outputs compared to the standard Python REPL and IDLE.  And the sidebar adds 3.5 characters' width only for outputs, which can be avoided when it's truly crucial using the "Copy with prompts" feature.  Overall, considering the benefits, this seems like a relatively minor drawback.