When someone opens the lockscreen of your HTC 10, they may see some notifications that are too private for you. So, what's the solution? To show / hide notifications on Lock Screen in HTC 10, do as follows:
1. Open the Settings app on your HTC 10
2. Scroll down to the Phone settings and touch to open the Sound & Notification settings
3. Scroll down to the Notifications settings and open the When Device is Locked option
4. Now, specify what notifications you would like to see on the lock screen: Show all notification content, Hide sensitive notification content, Or Don't show notifications at all.