Correct behavior should be that, when $event is not null, $~event and $$event should be the same as $event.
I notice that you have made several references to $~ in your posts. This is used internally by the script parser and changes how a parameter is parsed in several ways. It should never be used in a script.
Regarding the rest of your post: I will be changing $$ so that it is processed in events. However, it is difficult to predict what the side-effects will be. $$ is an ancient prefix and the scripting language has evolved around it. If the change has negative side-effects, I will be reverting the change.