If you don't have an asynchronous queue driver I believe there's a 500 error when posting when the Pusher limit is exceeded, no? It's the same kind of error if an email fails to send. The post will be created, but the user will see a 500 error and some extensions might not be able to run their logic on the event.
When an async queue is setup (using Redis for example), then the error will happen inside of the queued job so the end user will not see it. Also it won't impact other queued jobs.
