Curious, why have guest accounts been banned? I recall being able to post as a guest in the past.
IMO, newbs don't deserve the privilege of a member account and should earn it.
I say this as a veteran newb who has used AHK since 2008 and still knows diddly shit.
New accounts have a number of limitations, like you might have noticed, which they didn't have in 2008. They get lifted after a certain number of successful posts. That's the way to earn a regular account.
Guests can at least post in Forum Issues - for example, if they have problems registering an account. No idea about the other subforums. But there are sometimes still guest posters. Probably 'Offtopic' is also open for them (if their posts get approved). One disadvantage of guests is that they might not find their post again, if it has to be moved. Generally, I would recommend registering.