There is no solution which is 100% perfect to stop the spammers misusing the gambling chat.
There are certain solutions that can actually restrict spanners to a huge extent, but that would require setting intense restrictions which could possibly drive away legit gamblers thanks to the strict rules which is why casinos think twice before implementing these rules.So many trolls trying to get more chances during these giveaways are getting way out of hand. If you watch an entire livestream done from stake you will know what I mean. 
The fact is that these scammers will find a way no matter what. However, they can be restricted based on the rules implemented which is why the current chat rule change is a welcome change.