The links you reference are very old, and one (actually for JDeveloper) predates the existence SQL Developer. The automatic reload works fine for me, both for Notepad and Notepad++. Since it also works for you with the 3.2.2 release, I can only assume your user settings for 4.0.2 got corrupted somehow. If you migrated them from 3.2.20.09.87 or some other release, I recommend...
1. Exiting SQL Developer
2. Deleting or renaming %APPDATA%\SQL Developer\system184.108.40.206.21
3. Keep in mind that Windows by default, considers the AppData folder portion of C:\Users\<username>\AppData to be hidden.
4. Start SQL Developer and skip past any prompts about migration of user settings.
Hope this helps,
SQL Developer Team
Thanks Gary, that's solved it.
And oops, didn't notice the dates on the links I included, sorry about that!