When Google introduced Android 5.0 Lollipop there was plenty to love and many new things to explore. It brought along new visual appearances with the Material Design style UI, and useful new functions like lock screen notifications and floating notifications. One thing that users seem to split down the middle on though was the new interruptions modes that take the place of how your notifications interact and alert you. Prior to the Lollipop update, users had the option to keep their phone on silent, vibrate, or with the ringer on. In Lollipop, things are completely different and notifications are classified as interruptions, with users having the option to set interruptions to all, priority notifications, or none. Alas, Silent mode is gone.
Now in Android 5.1 Lollipop, Google seems to have in some way rectified the loss of silent mode for the many users that were sad to see it go, and has introduced LED indicators for the notifications for all modes, so that means even when you set your interruptions to none the LED light will blink when notifications come in. More or less, this is Silent Mode. The phone doesn't ring or vibrate when interruptions are set to none but the LED notification will blink now with Android 5.1, which is exactly what happened when silent mode was active in versions of Android prior to Android 5.0. The only difference is that setting interruptions to none still hinders the alarms.
On the other hand, there are plenty of users that loved the idea of no interruptions at all(including the notification light)with the mode set to none and would at least like the ability to turn the LED notification light off. When users are sleeping for example, this is a perfect time for when the LED light should have the ability to be turned off. Whether or not Google will patch in this specific tweak is unknown but it seems like a feature users would want, at least according to some comments on reddit. For users who don't like "none" because it hinders alarms, you can set interruptions to none "until next alarm" which basically fixes that issue. This isn't really a true silent mode in the old way but users now have more control over the way notifications are handled, and more control is never really a bad thing.