If you mean Jot Messenger, then yes. Vendor of the Talk (person who has created it) or administration of the site, can edit and remove any message for the talk. To edit message you need to double click on it (for desktop versions) or using message's top right menu and then click on Enter or Save changes button.
I'm talking about the messenger feature in the site we're currently on. I'm fairly confident I don't have administrative privileges at una.io but I can go into my messages and change what people have written to me.