You can set whether to show senders and message contents on the lock screen. Both of these settings are persona-based.

Show Sender Name - to show the senders’ names on lock screen
To enable preview of sender’s name, please go to Dashboard > enter a specific Persona > Tap the setting icon on the top right corner > “Notifications” > Turn on Sender Name.

Show Text Message - to show the contents of text messages on lock screen
To enable text message preview, please go to Dashboard > enter a specific Persona > Tap the setting icon on the top left hand corner > “Notifications” > Turn on Text Message .

On the other hand, you can also disable both settings together, so both the sender’s name and text message contents will not be shown on the lock screen.