Nowadays I start to wonder why people use the registry so much. Yes in case of things you like to share with other applications its nice but if the settings are only used by the app itself I rather see it stored in an ini in the application folder. This because that would make the application 'self contained' en even used from an USB stick and keeping all settings etc.
The bad thing of the registry is also that many applications leave their settings behind after uninstalled making the registry fill up over time with (now) useless data.
Please consider having all user settings put into the application folder only, for easy portability of Sigil and a clean (windows) environment. Thanks