Many people post questions on these forums that have detailed answers in articles and blog posts from people who aren't Apple employees. It would be nice to link to these articles when answering questions on these forums.
But if you try to link to a non-Apple URL, you get an error message that the domain is invalid. To post the link, you have to remove the https://www part of the link. This forces people to cut and paste the URL into the browser to read the article when they should get a clickable link.
If you're worried about spam links, then either require posters to have a minimum reputation score or have a minimum number of posts to submit answers with external links.
