As a user of the new discussion software, I would ideally be able to perform all actions that are currently possible with the current software (aside from rearranging elements on the page and such). This includes, but is not limited to:
- Replying to all comments
- Creating new discussions/sections
- Adding a new comment in an existing section without any comments
- Replying while also introducing a level 2/3 header on the page before the reply (or the equivalent/corresponding functionality for any new syntax introduced)
- Replying after a subheader within a discussion (or the equivalent/corresponding functionality for any new syntax introduced)
- Replying at the bottom of a discussion/section without having to search for the parent comment on the page (particularly in long discussions)
- Choosing the indentation type (:/*/#) for a comment or a discussion (or the equivalent/corresponding functionality for any new syntax introduced)
- Hiding or collapsing part of a discussion (e.g. a comment and all of its replies)
- Closing a whole discussion (i.e. the "Mark as resolved" action in Flow)
These are all commonly done in discussions on the English Wikipedia. My understanding of the version 1.0 mockups is that only the first action will be possible with the 1.0 software, since it will only be possible to surface the interface by clicking the "reply" buttons.
Regarding actions 5 and 6 specifically, consider the addition of a support or oppose vote to an English Wikipedia RfA. The "reply" buttons will be at the top of the page, after the candidate and co-nominator statements, and will be separated from the actual vote and discussion sections by all of the questions for the candidate and at least one subsection header. It would be possible to handle this sort of issue without a software change, but users would be forced to add superfluous top-level comments at the start of every subsection for every RfA (as well as every RfC, XfD, etc.).
For usability and convenience, it may be desirable to allow users to perform more than one of these actions at once with the new interface (even if they're unrelated to each other), as opposed to requiring them to be done as part of separate edits. (For example, this could take the form of allowing users to add multiple sections in the same edit.)