The ability to enable/disable various alerts is now available in your control panel. In the upper right corner, click on Settings, then scroll towards the bottom. On the left, you'll see some settings for User Tagging. It looks like this:
Quote notifications have been re-enabled. If you don't like them, you can now disable them on your own. Additionally, we're in full Twitter mode. You can now
#HASHTAG a thread, and subscribe to hashtags in your control panel. I expect this feature to never be useful here.