On posting directly to a megathread ... thanks! While this is good, and has already happened in megathreads (I forget which I saw it in), it doesn't lean into the federation of content that can happen which is what I'm trying to see more of. That is, not just "cross-posting" but the same thread existing on two platforms simultaneously in much the same way lemmy communities exist on multiple instances simultaneously.
Otherwise, happy to talk about the mastodon<->lemmy "cross-posting".
Here's a basic demo I've written, posting from Mastodon to !test@lemmy.ml : https://hachyderm.io/@maegul/110483509521476095
And here's the view of the post on lemmy: https://lemmy.ml/post/1142168
You'll see that both lemmy and mastodon users can comment or reply with the only difference being how the two platforms display the threads (lemmy doing a much nicer job IMO)
The key machansim is that lemmy communities federate to mastodon as "users" that can be "at-ed" like any other user from mastodon. Lemmy then interprets such a post as a new post to the "at-ed" community, takes the first line as the title and the rest as the body. The only trickiness is that lemmy will only pay attention to the first "at-ed" handle, to prevent cross-posting and spam.
What I initially imagined was that someone could start their own journalistic megathreads here by doing exactly the above and then replying to their previous post to create a thread on mastodon and a chain of comments to a "megathread" post here on lemmy. This would be the easiest for the person posting from mastodon.
The difficulty for you is that it would be a post that isn't necessarily to a news source, but just a stand alone post ... though the person I'm asking on behalf of is almost always providing sources/links.
Beyond that there'd be your policy of confining all Russia-Ukraine war stuff to the megathread. On this, they could reply to the megathread and basically embed their mastodon thread within the megathread. This would work well. It's just that finding the megathread from mastodon and replying to it can be non-trivial and may not be available all the time.
For instance, I can't find the current megathread on my mastodon account and I don't know why ... it's probably an instance visibility problem and will get better now that I've subscribed/followed world@lemmy.world from my mastodon instance. So this may become a good way forward without much hassle.
As for the kind of threads I'm thinking of ... here's an example: https://hachyderm.io/@mariyadelano/110599817912125441