Can you disable the delete message button in the chat room for users?

If you want to disable the delete option for users, you may add this CSS code under Settings > Advanced Design > CSS for Web Browsers.

body:not(.moderator) .delete-own-message,
body:not(.moderator) .delete-all-message {
    display: none;
}

The delete option will not appear when you click the three buttons on each message box (kebab menu).

You can also add this CSS code if you want to remove the three buttons (kebab menu) altogether.

body:not(.moderator) .message-text-container .menu-wrap {
     display: none;
}