I have noticed that all substack pages use <a href... rel> links, meaning that every <a> tag on a page hosted by substack closes with rel> and not > or />. It doesn’t appear to be a correct html code to me, neither it is the proper rel="?" property for a link tag, what could that be then?

I tried to search for an answer on web standards sites and interrogate chat gpt, but everything points that it’s either a bug or a “inside” tooling of substack