There's nothing intentional there. If the keyboard you had installed was also distributed via F-Droid using the same APK identifier, then F-Droid just detects a

There's nothing intentional there. If the keyboard you had installed was also distributed via F-Droid using the same APK identifier, then F-Droid just detects an update since it's the same app. To prevent this (it can happen with most apps distributed both on the play store and F-Droid) you can tell F-Droid to ignore updates for a specific app.