In the FAQ, it is not clear that there is a rep limit before a new user can post URLs. This may lead some people to believe that a newcomer without rep is forgetting linking URLs, may result in unnecessary downvotes or rude comments.
While I think this limit is a good measure to prevent spam, I believe it must be documented. I personally learned it from a comment to a "linkless" answer.
Related: How does "Reputation" work on Stack Overflow?
Documents the reasons for the gains and losses of reputation but not the limitations.