While there are default configuration files in /etc the 'real' configuration is made by the user. It is common practice, that no package is allowed to remove something from the user's home directory. This is were the config files are stored. So the settings from the last time will be used if you reinstall a package.
If you want to get rid of all the remainders, you have to find and delete the dot.folder or dot.file in /home/user.