Can I delete a guest book message?

Yes: as the host you can delete any typed message or video greeting from the guest book with the trash icon next to it, and it disappears for every guest at once.

Your browser is the host's when you created the event in it or opened the host link from your confirmation email; on another phone, tap Download all on the event page, enter the code emailed to the host address, and that phone is recognized as the host's too. The guest book sits under the gallery on the event page, and the dashboard links straight to it.

Deleting asks you to confirm, because it cannot be undone: a typed message is gone, and a deleted video greeting is removed from the guest book and from any ZIP you request afterwards. Guests cannot delete entries, their own included; they can only edit their own typed message from the phone they wrote it on.

There is no approval step and no way to hide a single entry without deleting it: greetings are visible to every guest the moment they are sent, so look through the guest book during the evening if you want it tidy. The guest book, like video, is part of the paid plan.