The bug seems to happen only when the script is created, exported to package, modified and exported to a different package

To reproduce:

1. Download the packages, attached by the tester (package1.unitypackage and package2.unitypackage)
2. Import package1 into the new project
3. A menu item should appear in the toolbar: Tools -> Class1
4. Import package2 into the project
5. Tools -> Class 1 menu item will be overridden and will show Class2 instead of showing both Class1 and Class2.
6. Both packages contain a differently named script in the Editor folder, but after importing both packages there is only one script

Expected: importing the package which contains a very similar script to a previously imported package's script, doesn't override the existing script

Reproduced in 5.5.4p2, 5.6.3f1, 2017.1.0f3, 2017.2.0b5, 2017.3.0a2

Won't fix: asset store package feature (.unitypackage) is deprecated in favour of the new Unity Package Manager. This bug user pain is too low to invest development time