Javascript scrolls to the target and the browser history is clobbered. I expect it now, but it was an unwelcome change.

The parent option isn't returning a new URL. it simply scrolls to the target. I don't see where it is impacting my internet history.

Try to return to the previous location.

FWIW if you hover over the parent link it is indeed populated with a different URL.

For some reference, this post is

https://news.ycombinator.com/item?id=37013396 (shortened to 13396)

my comment you replied to

https://news.ycombinator.com/item?id=37020429 (shortened to 20429)

and your comment here is

https://news.ycombinator.com/item?id=37020517 (shortened to 20517)

I think the issue depends on whether you are on a a comment URL (e.g. clicking on the timestamp of a comment), or if you are on the post. If I'm scoped into 20517, the "parent" option is indeed a link to 20429. It will hard load to scope into 20429.

But if I'm on the actual 13396 post and click parent on your comment, I am instead 'loading' 13396#20429. Which of course isn't reloading the page but scrolling to a specific header.

I never personally liked the decision where replying or loading a comment took me to a whole new webpage instead of rending a formbox within 13396 and/or loading 13396#[comment ID], but I imagine there were historical and/or technical reasons for the decision. It generally doesn't bother me as I tend to mostly browse comments and only occasionally respond.

   I am instead 'loading' 13396#20429. Which of course isn't reloading
   the page but scrolling to a specific header.

No, you're scrolling to that via javascript. Previously this was handled by not interfering with the link to that URL thus preserving history and your location on the page.