The only indication that an email is not required is that the email field doesn't contain a blue dot, as opposed to the username/password fields. However those

The only indication that an email is not required is that the email field doesn't contain a blue dot, as opposed to the username/password fields. However those are on the next page, so you have no indication that it's not required. That's actually on the new design, on old.reddit.com there is not even that indication.