Same question that i just asked support today and they came back with the following. As we heavily customise our Page Layout, i’ll need to get our 3rd party support to do this part so it doesn’t affect the overall look and feel. Feel free to give the below a go though in Sandbox (just in case)

Please navigate to Admin --> Helpdesk rebranding --> customise portal -->Layout and pages --> and paste the below code in the Page Layout box.

<script>
  jQuery(document).on('SideModalOpen', function() {
setTimeout(function() {
  jQuery(".request-someone-container").hide();
  jQuery("#requester_email").prop("disabled",true)
        });
   });
    </script>

Another easy approach is to hide the checkbox itself by adding the below script in Admin → Helpdesk rebranding → Customize portal → CSS

bodycpage="catalog_item"] #side-modal #side-modal-content .place-request-container .request-someone-container .request-container {
    display: none;
}

Thanks Glavin. That worked very well.

this hasnt worked for me 

i copied into the stylesheet page in portal customisation 

please help

bodydpage="catalog_item"] #side-modal #side-modal-content .place-request-container .request-someone-container .request-container { display: none; }

Hi all,

I want to do kind of the same.

But at the report issue/submit ticket page

When requesting a ticket I want the requester not to be able to request for someone else (hide or disable).

But I want to keep te CC option.

Is that possible?

bodycpage="catalog_item"] #side-modal #side-modal-content .place-request-container .request-someone-container .request-container {
    display: none;
}

Worked like a charm! Thank you @Glavin Crasta !

Also, for anyone who wants to disable the ability to edit who is requesting a Service Item, this works as well:

/* Disables editing of the "Requester" search field in Service Requests*/
body*page="catalog_item"] #side-modal #side-modal-content .place-request-container .requester-field-section .req-search {
    pointer-events: none;
}