The Brand New accounts, were they restricted from creating a new thread as their first post? And, if this is true, wouldn't they only need to do one post to "rank up" and remove this restriction?
No.
Brand new accounts can create threads with their first post. (Except new changes have been made and I missed the announcement).
And the restriction can be easily bypasses, even by bots, reason why it would probably not be implemented.
I would really appreciate the help, I needed the info for a project I am currently investigating, where the dev claimed they created an account (currently on BN rank) but they can't create ANN, and someone had to give his old account to the team so they can publish the ANN using said acc.
New accounts are limited from posting embedded images and have to wait for a cool down time between posts, but they can start their posting with a thread.
Does the old account have a negative trust rating?
Is the old account a Jr member ranked or above?