Usually you can quickly click through the different changesets and see all the old comments. In my experience, it maybe needs one more click to follow the reference compared to similar comments referencing the current changeset.
Answer, just like with the non-changeset oriented workflow, it depends. If the new PR update deletes the associated lines of code, there is arguably a need for those types of comments to be manually added with the current interface, but not so with a changeset oriented interface.
I like the append only nature of a changeset oriented interface.
But I find this type of conversation quite fiddly to do in pure text without reference to examples and the actual use of both styles, so forgive me if this is still unclear.