You should only use moderated search indexes in production, or <x id="START_LINK" ctype="x-a" equiv-text="<a href="https://framagit.org/framasoft/peertube/search-index">"/>host your own<x id="CLOSE_LINK" ctype="x-a" equiv-text="</a>"/>.
This is just an extra information injected in PeerTube HTML that is required by Twitter/X. If you don't have a Twitter/X account, just leave the default value.