This has just happened in the last couple of days. It was after:
Could either or both of these caused the issue? Is there a way to have the site remember what I’ve read…or was that info lost forever when I cleared my browser history? Thanks.
What you’re talking about is the “visited link” feature all browsers have. That if you clicked on a link once, it will be shown in a different color to show that you’ve already clicked it before.
But if you delete the browser’s history, that info (which is stored in your browser itself) is lost.
However, the site has it’s own feature to mark stories you’ve already read, it’s that blue or green checkmark on the title:
It appears if you’ve spent sufficient time with a story and scrolled all the way to its end. That way, the site assumes that you’ve read it and add that mark. It’s blue if you also rated the story, otherwise it’ll be green.
That only works if you’re using an account on the site and you need to be logged on when reading stories. But it’s stored server site, so even if you use another computer or browser, or delete the browser’s history, that info will remain intact.
Thanks, Martin. That explains everything. My habit is to put links of interesting stories in my Reading List in Safari for later reading. Those which are there but still unread used to be greyed out when I went to the main page. That is particularly useful when a new chapter in a series appears; I know I already have the series page in my Reading List and don’t have to click it again. Anyway, I can do a workaround until I actually get to read the already saved links from before my history-clearing.
Well, you know that there is a bookmark feature integrated in the site for that very reason? 
Don’t hesitate to ask if you want me to show you how it works…