I made a thread about it some time ago but to make a long story short; The more time you spend on the forums and participate in discussions, an invisible rank that is known as your “trust level” increases. There’s 4 ranks and everyone starts at level 0 and get up to trust level 3. The more levels you have, the more things you can do. Links to anywhere are a perk at the highest level.
For those who don’t have the rights, there is a solution; putting the link in a code block by pressing the </> button when making a comment.
Here's a gif to show how it works. (Click me!)
www.google.com ← Like so.