Both Slander and Libel are a very difficult thing to prove, and therefore expensive, so it tends to be celebrities with loads of wonga who push cases through the courts - and usually these are copper bottomed, cast iron cases.
Anyone seeking legal recourse would have to prove that by putting his post up stating that Soussan was a Liar / Cheat / Thief, Paul had altered everyones opinion of Soussan to the detriment. Since it's common knowledge/popular opinion that Soussans dealings have been less than above board this would prove extremely difficult.