What are you talking about? I just did "echo 1,2 > test.csv" then opened test.csv in OpenOffice Calc, then saved it as test2.csv from the save dialog. No complaints. Then I clicked to close it. No complaints about unsaved changes. Did you actually try that out before you commented? I don't have any of the other programs you mention on this computer, so I'll pick another - let's try OpenOffice Writer. Made a text file, opened it, saved it as a .txt file, it asked me for the encoding, I confirmed it, I clicked closed, and it closed without trying to force me to save as an .odt.
I'm sorry, but GIMP's change is totally broken behavior. The most common workflow for GIMP (as you can see from all of the rage on the forums when these changes occurred) is not long complex workflows, but simple changes to jpegs or pngs. Open, change it, save it, close it. What sort of moron do you take people for to think that you have to "protect" them from choosing a format of file that doesn't save layers, and instead try to make them always save whatever they do in a format that no other programs support? As if a dialog warning them that it doesn't save layers and asking them if they want to flatten it, like Gimp used to do, isn't enough? What on earth is the point of *banning* people from typing in a file with the suffix that they want to use in the save menu, and instead making them choose an entirely different menu? Actually two different menus, depending on context, only one of which has a keyboard shortcut. It's just ridiculous. We're not preschoolers, we don't need the hand-holding.