So reinstalling the whole OS was higher up the troubleshooting chain than just trying it out from your wife's computer? Err...
If you've never done the equivalent, it's only because you haven't been around computers very long.
Dude, in twenty years with computers I have never re-installed an OS to fix a problem (obviously this is distinct from installing a new version of the OS which could legitimately have a fix for it). For me rebooting the computer is even a last act of desperation that I am ashamed to take.
But then I am a unix/Linux user. I grant you the possibility that this may somehow have been a rational act for MacOS, though if true I find that disappointing.
I think you are suggesting a non-causal solution. What exactly is this "it" you think I should have tired on my wife's computer? The character never appears in my normal mac usage. So despite the fact that I use her computer all the time, I never noticed it happening (though I'm sure it did) from her computer.
At the time, all you had to go on was that there was a probable misconfiguration somewhere in the deep, dark innards of MacOS, and the best way to handle that particular problem is to nuke it from orbit.