As far as I’m aware, Rank restriction to post apply only the previously mentioned Serious Discussion and Ivory Tower boards, as well as to the Investigations board. Whilst the former two mentioned boards do allow you to read the content within whatever your rank (not post, as mentioned in @hosseinimr93's quote), the latter, Investigations, can’t be accessed, even to read it, until you reach Member Rank.

A few related additional things to consider would be:

- You need to become a Jr. Member (or acquire a Copper Membership) to post visible images on the forum.

- Posting frequency is limited by your Activity (not Rank), as per the following formula:
Essentially, you start-off with a 6 minute cool down time between posts, and as your Activity increases, it can go down to 4 seconds between posts.