From what I can see, the old DPReview forum utilized a really old school method of threaded/nested conversations on a thread-view point of view. To be honest, it is probably along the lines of late 90s, early 2000s style of nesting. That form of nested comments/content I've almost always regarded as a 'threaded overview' is based solely on nested headers, extremely similar to mailing list nesting of constant "RE: RE: RE: RE: Subject Name' in response to the original user emailed styled nesting. While there's nothing wrong with that, that particular style of nested discussion is quite confusing to current-day internet users, and
is legitimately dated.
The newer generation of content nesting doesn't utilize a discussion subject, it just attaches to the parent comment. Numerous platforms across the internet, big and small use this newer style of comment nesting. It's also a layout that I personally do not mind, as it keeps sub-discussions to the overall thread of discussion/submission generally on topic and in order without causing too much of an end-of-thread-discussion-hijack (a linear thread issue). Effectively the newer generation of comment nesting includes the content "right then and there", and no longer requires additional clicking to begin reading.
The old style that they had was legitimately overwhelming due to the sheer amount of nested discussion links without a logical display-culling limit set in place.
A decent example of quite the nested thread layout:
http://web.archive.org/web/20210514064424/https://www.dpreview.com/forums/post/65047483
Same thread but in flat mode:
http://web.archive.org/web/20211024...com/forums/thread/4568381#forum-post-65047483
TL;DR: Threaded/Nested comment chains work better on some platforms, while linear comment chains work better on different platforms. Best of both worlds is to support both modes, but that's exceptionally uncommon.