Accessibility: native comments threading not visible to screenreader

Issue Summary
Love that we have native comments now, thank you! To help improve:

Comment threads are only marked in a visual way. So someone that cannot see the layout is not told which comments are threaded. This is an accessibility issue, for example, if you are using a screenreader.

Further, the “…” button to select report is not clearly labelled for a screenreader (e.g. with an aria-label).

Steps to Reproduce

Tested using a screenreader.

Setup information

Ghost Version
Ghost Pro Aug 24 2022