This is at least 2 issues: startup and restart. I closed #8378 as a partial duplicate of the startup issue.

For startup, I reject the idea of changing the default and the meaning of -s. First, it would break the general back-compatibility policy and possibly break scripts of people who read the doc and proceeded accordingly. Second, while I generally prefer Idle to match the console interpreter, there is an important difference in having tkinter and idlelib modules involved. A startup script that works fine for the console could create subtle bugs in Idle. I suspect that whoever chose the current default had some thought like this. To put this a different way, running idle is similar to running 'python -i idle' and python does not run startup files with -i. Third, this change shuffles responsibilities around without any net gain that I see.

#5594 suggests adding startup options to the configuration file and dialog. I like this better and consider it possible.

For restart, the result of Restart Shell Cntl-F6 should be the same as an initial start (without running a file from the editor). On the other hand, I agree with Beni's concern about matching python -i when running editor files.

I also agree with Beni that the run... functions should be reviewed for possible refactoring, and, sadly, that testing is difficult. We would need a test script that documents both current and desired behavior and people to run it (by hand and eye) on Windows, Linux, and Mac.