Gmail's special character parsing

Here's a lesser known behaviour of gmail usernames:

If you've a gmail ID that goes A.B@gmail.com (for example), you can email AB@gmail.com and still receive it. Or vice versa. Give it a shot. I just did this week and to my amusement, the email was succesffully delivered to my A.B inbox. You cannot sign in with the alternate ID but you most definitely can receive mail!

The simplest way of achieving that is by parsing out special characters and leaving only the alphanumerics internally. Any 'To' gmail address would also be then parsed out and matched against this database of alphanumeric IDs. Why? To keep it simple, I'd assume.