LPS-42608 When a user changes the configuration of a non-instaceable portlet whose prefs are owned by the group within a customizable column, the changes affect all users.

This is the minimal solution, which prevents the user from changing the configuration in this scenario, since it's not supported.
LPS-42608 For non-instanceable portlets with preferences unique per layout it should be possible for each user to have its own configuration within a customizable column.
LPS-42608 SF