There's still a memory leak in SignalR I'm trying to figure out how to fix or workaround. If it's an extremely horrible experience, you can disable them under your account. You'll still receive them in the notification inbox, but not in real-time.
Judging by the responses, it seems to be a [majority] Firefox issue (works great in Chrome). I fear it's the same problem FF users experienced 10 versions ago with ASP.NET MVC and something related to IPV6.