You’re right. Deleting the App Store version of Folding Text using Launch Pad deletes the sandbox and everything with it. Whereas removing the application from the /Applications folder keeps the sandbox data.
I didn’t realize Folding Text needs to check for the sandboxed App Store receipt on every launch. I thought that once it checks for it, it would write that in its own license file and never need the sandbox or receipt information.
I know of another app that follows the same method you do. I purchased Kaleidoscope (http://www.kaleidoscopeapp.com/) on App Store, and then downloaded the non-App Store version. After the first launch, it detected the purchase receipt, wrote it down in the prefs file and then I completely deleted every trace of the App Store version.
Do you think something similar would be possible for Folding Text? I’m curious, is there anything stopping you from generating a license on-the-fly when you detect the MAS version?
This doesn’t seem like a critical issue, please take your time. I’m really liking Folding Text at the moment.