But first, just to put the final nail in the coffin – Google’s Support Response
Thank you for your message.
Gmail doesn’t recognize dots (.) as characters within a username, so you can add and remove them for desired address variations. For example, messages sent to firstname.lastname@example.org and email@example.com are delivered to the same inbox, since the characters in the username are the same. Gmail allows only one registration for any given username, so dot variations of any username aren’t allowed. In your case, you are the sole owner of both firstname.lastname@example.org and email@example.com.
If you believe that a message was accidentally sent to you, we suggest contacting the sender to inform him or her of an incorrect address.
For your protection, you can only log in to Gmail by entering the exact username you used to set up your account. If you entered dots as part of your username when you signed up for Gmail, please enter them each time you log in to your account.
The Gmail Team
I actually received this response a few days ago – just haven’t had a chance to post until now.
While it’s good to know I’m the only one that has all the variants of my account, the “In your case” concerns me just a bit as it doesn’t speak to an overall inability for different people to have registered the same accounts at some point in time. For now though I’m just going to write it up as words that were used not knowing the bigger context of this answer (i.e. the admitted blogging disaster that was last Friday).
All I can suggest is to email Google support if you have a concern about getting someone else’s mail – as this response indicates they’ll clearly confirm if you’re the only person with that account.