For AMAs, it is absolutely critical that all official replies quote what they are replying to, like so:
here is my official answer
That’s the one bit that must be right, otherwise all is lost. If the AMA owner is just tapping the reply button without quoting (or not pressing the reply button at all) you are screwed.
I could see having an optional topic setting that forces all replies to one level (no multi-level, just one) and docks them under the thing they are replying to. This would completely destroy conversation chronology, but it would make AMAs, or any other “in this topic, we shall discuss absolutely any random topic at all with no limitations” topics, easier to deal with.