I haven't had issues with the dot feature but have run into problems using plus. My problem was that I used a "first.last+website@gmail.com" format when I sign

I haven't had issues with the dot feature but have run into problems using plus. My problem was that I used a "first.last+website@gmail.com" format when I signed up for a website and some time later I needed to contact customer support by e-mail. They had no record of my account because my e-mail came from "first.last@gmail.com" and not "first.last+website@gmail.com". It turns out there is a way to send mail from "first.last+website@gmail.com" but I don't think it existed at the time.