Preorders are now automated, so preordering gives your forum account immediate access to the game. It also sends a preorder confirmation email to the payer (finally). This works both if you preorder before creating an account, or if you preorder after. Multiple preorders accumulate subscription time.
(This is not a good time to preorder, however, because the new server is down until I release a new client build.)
This applies retroactively to existing preorders. Your preorder months are now visible in your profile (the link with your username at the top of the forum) under "About" > "Subscription". You can see whether other members have an active subscription, but you can only see the number of months for your own.
Please let me know if you notice any bugs.