So... the first thought is that edit summaries shouldn't be needed at all with talk pages in general and with Flow in particular.
But on a second thought, they may be useful. A Hebrew Wikipedia user said: "If from the edit summary I see that it's a welcome or a warning template, then I don't bother checking, but if it's a reply to a post that interest me, then I do. And sometimes talk pages are vandalized."
So I'm passing this on - although maybe the right thing is not to add edit summaries, but to somehow understand the different workflows and indicate them in recent changes and watchlists accordingly.