[naner]

The dot doesn't matter to gmail. It matters to other services. Way back when I first learned about this feature, I registered for some website using [e-mail].

Unfortunately, when I later had to verify my account through email (as opposed to clicking a verification link) the website did not recognize [e-mail] (my sender address) as the account owner.

[pasbesoin]

It does matter to Gmail, when signing in to its web interface (as opposed to email addressing and delivery). Or, it used to. Even though you could not create account names differing only by the presence or absence of a period, when it came time to sign in, you needed to use whatever variant you used when you created the account. (In my very limited experience, at least. Account created as xxx.yyy at gmail dot com needed to sign in to the web interface as xxx.yyy, Gmail would not accept xxxyyy as the user ID for the account.)