I think it is better to discuss refactoring features that make sense inside Flow. There is no plan to migrate classic talk pages to Flow, and there is no compatibility plan at all either. In fact, restricting wikitext's free-form editing is one of the explicit goals of Flow.

So I went through the long thread that you link and I extracted the features that I think make total sense in a Flow future.

• Move a thread to another page
• Move a comment to another thread (in the same page/in another page)
• Split a thread in two.
• Merge two threads.

PS: I'm not a Flow team member, I have no influence in their plans, I just happen to love Flow, and I want it to succeed.

In that list, we missed some features. For instance, these ones:

• Split posts
• Indent and outdent posts
• Re-sign posts for another person
• Split one thread in two threads (and give a new topic the new one)
• Support nested threads (2 threads inside of one with relevant subheadings)
• Edit timestamps on other Flow posts (i.e. I split it into two, but I would like to set the new post timestamp to the real old ts, not to now)

They are immediately useful for the goals I'm describing, as well as for handling a moderately big RFC.

In T78253#842965, @Gryllida wrote:

In that list, we missed some features. For instance, these ones:

• Split posts

imho too complex for little benefit. Anybody can quote somebody else's comment (or your own) in a new comment.

• Indent and outdent posts

I wouldn't bother.

• Re-sign posts for another person

In normal Flow use this doesn't make any sense. You justified this in the context of a migration from wikitext pages, but that won't happen.

• Split one thread in two threads (and give a new topic the new one)

It's in the short list proposed.

• Support nested threads (2 threads inside of one with relevant subheadings)

I don't think this fits with Flow's explicit simplicity. But merging threads makes sense; I will add it to the short list.

• Edit timestamps on other Flow posts (i.e. I split it into two, but I would like to set the new post timestamp to the real old ts, not to now)

We should assume that timestamps are kept when moving threads and comments.

They are immediately useful for the goals I'm describing, as well as for handling a moderately big RFC.

Since my list is included in your list, why not starting there? :)

It's ok. Our two messages give an idea. I don't care where to start. (The timestamp editing is needed for refactoring things, a point you missed, but I have the impression that the Flow folks understand what I mean.)

In T78253#843089, @Qgil wrote:

In T78253#842965, @Gryllida wrote:

• Indent and outdent posts

I wouldn't bother.

This is the most important one for me, when people click in the wrong reply button, and their reply gets positioned below a comment which is completely unrelated.