I think this is by design. There are two shortcuts in Crimson editor related to this:
- F3 - Find next
- Shift + F3 - Find previous
This guarantees that when you hit F3 you will search down the file and if you hit Shift+F3 you will search up the file regardless of whatever you put in the Find Dialog. So it's not necessarily a bad thing, it's just how it was designed.
Also since I'm not a huge fan of Windows Notepad I tested Notepad++ and UltraEdit and they pretty much have this feature designed in the same way as Crimson Editor with minor implementation differences.
So yes, this is how it supposed to work.