It’s also useful for avoiding accidentally misaddressed mail. For several months, I was getting lots of email intended for an American lady whose email is identical to mine apart from an initial in the middle. Unfortunately, the initial was the same as the last letter of our mutual first name and a lot of people just missed it out as a result, because they didn’t ‘see’ it.
I suggested she give out her email address with a dot on either side of the initial, and it seems to have worked like a charm. The initial stands out clearly and people are obviously remembering to use it now, as I haven’t seen an email for her in several weeks.
It’s slightly scary how much you can learn about someone just by getting random mail intended for them. Luckily, this lady seems a very nice person.