This might be old news, but I just found out about it the other day. I actually found out about it coming from a different direction.
I checked to see if two Gmail user accounts were available, one with dots and one without.
For sake of illustration, let’s just say I checked the availability of:
Both were available
I created an account with the user name without the dots. Worked just fine.
I then went back and tried to create the username with the dots. No dice!
Apparently, dots are ignored or skipped over or treated as an empty character because Gmail is treating “abcdef” and “abc.def” the exact same (I really doubt someone else took the “abc.def” account in a matter of 20 seconds after I created the “abcdef” account).
I just found this strange.