This information about this is in the Help Center, https://drupal.stackexchange.com/help/abuse-block:
In an effort to maintain the quality of our collaboratively edited
resources while imposing the fewest possible restrictions on who can
create and edit content, Stack Exchange utilizes several layers of
While our systems are still learning to trust new users, additional
positing limits might be imposed if the system detects that a large
amount of spam or abusive content has been posted from others
utilizing your Internet provider in your area.
and for the particular message your friend saw:
It means that the abuse was extremely severe, and that we
unfortunately can't accept your contribution until the abuse has
subsided. Unfortunately, in most cases, this will mean that you need
to contribute to the site from an alternate location until a few of
your contributions have been well received by the community.