Should one respond to a suggestion with another suggestion?
We framed the feedback mechanism as "suggestions" because we want comments to always be focussed on how to improve the proposal, rather than getting sidelined into discussions within themselves about minor points. That said, I understand your confusion.
What I'd recommend is that if you're the proposal author, you try to update your proposal based on the suggestion, if you think it has merit, and then leave a comment in the suggestions box about what you've done/agreed with/disagreed with.
I also think it'd be good to have guidance on the scope of a talk,
Of course, this mailing list is absolutely the right place if anything about the process isn't clear, or if you have any ideas about how to improve things.