The workspace allows links as all of the discussion regarding terms and payment has already happened. The reason links are not allowed in the pitching stage is due to a lack of security caused in doing this.
In regards to communication about terms and payments being kept through our site, you have access to agreements made at any time meaning that in the unlikely event of a dispute we can provide evidence. Links may include alternate ways of contacting each other. If the important discussions are made outside of our site we are unfortunately unable to backup any claims you may make over discussions/terms agreed between both parties involved in a particular project.