Earlier quoted context omitted.
It does lead to people sending mail to the wrong address, from personal experience since Gmail was in beta. I've gotten sensitive emails and account signups with different dots for years. But the cause of that appears to be user error -- people thinking they own email addresses that are not actually theirs.
That's the point I think, the dots aren't causing any issues here, some people just assume their account is f.m.lastname@gmail.com and many of them are too stubborn to accept that it's not. They never had an email address with or without dots that's made up of the same letters as your email address. Their email address is probably very different (maybe they forgot to add a number, or a middle initial, or typed Gmail…
I've spent way too much time thinking about this.
Well, specifically about the kind of person who would use an email address they don't own to (a) buy a house, (b) apply for a FL sheriff's job, (c) conduct financial transactions, etc. (all actual examples I've received).
You think you have a bead on how ignorant people are, and then you realize there's a long tail you weren't aware of...