If you want to make sure(*) that the names are stored in the database with lower case letters, you can override the model’s save method to convert those fields to lower case before the save occurs.
*Note: This isn’t perfect. Bulk operations don’t call the save method on the individual rows being created or updated.
Warning: I know you’re not specifically talking about email addresses here, but there’s a real problem with the example that they’re using. According to RFC5321, the semantics of an email address before the domain name (the part before the @) are left to the discretion of that email server. It is perfectly valid for an email server to provide case-sensitive email addresses.
It is not valid to assume that the local component of an email address is case-insensitive.
(And yes, I know of at least one specific case where this is true.)
Ken