> One weakness I have noticed in NodeBB's current federation is that posts which are in reply to a topic (e.g. a Lemmy comment) show up as individual threads until (or if) the root post of that topic shows up in the local NodeBB.
No, Lemmy does not implement either strategy, they rely on 1b12 only.
If NodeBB is receiving parts of a topic that don't resolve up to the root-level post that might be something we can fix. I'll try to take a look at it.