i am runnig pro sites and remove email verification plugin and recently activated an ssl cert on my multisite installation.
new users only get logged in automatically if SSL is off and if i DON'T force SSL on checkout.
Another issue is, that if i have SSL active the subsite at the end of the registraition process also shows the link as "https://" but i don't use ssl on the subsites (See the screenshot below).
It also first looks like i am logged in if ssl is on, but after i click on either the created subsite or any other menu item on the page, i am logged out again. everything is working fine if ssl is deactivated.