Here are the steps you need to follow to hide your cards and your comments.
Step 1. Click on the clockwork icon (settings)
Final Step. Now select the "Hide cards" option to hide all your cards and comments from other people.
Note: When you hide the cards, participants will only be able to see the cards and comments they wrote. And you'll only be able to see the cards and comments you wrote.
You can reveal the cards and comments just for you by clicking on the "Show cards only for me" button.
After everyone finished writing cards, you can disable the option to "Hide Cards" to show all the cards and comments again.