If you want to add certain setting to individual users, create a directory that will have the settings of those users:
Edit vsftp configuration file to read that directory:
sudo mkdir /etc/vsftpd_user_conf
and set the user_config_dir variable (non-existent in the default configuration file) to read that directory:
sudo nano /etc/vsftpd.conf
Inside the /etc/vsftpd_user_conf directory, create a file named with the username of the "exception" user and set the variables/options that you want him/them to have as exceptions to the default configuration. For various users, various files, each one with different settings if you want.
Don't forget to restart vsftp each time you change its configuration
sudo /etc/init.d/vsftpd restart