Comment 10 for bug 1958670

Yeah, the macOS save dialog definitely adds in the extension by default, but I'm not sure offhand what Windows does.

If Pinta can successfully load files that don't have an extension, it's less of an issue. However, wouldn't those files might be subsequently filtered out in the Open File dialog by the "All Images" file filter because they don't have an extension? (making it seem as though the file might have disappeared).
I still think it's a less than ideal user experience - unlike e.g. a text editor, I don't think there's a good use case for saving an extensionless image in the vast majority of use cases