Yes, it won't happen going forward and there's not much we can practically do about it, I think it's fairly isolated though.
Our developers had this to say about it;
At first glance it looks like some kind of threaded reply in the old platform tripped up the migration script. We can't go back and reimport content at this point though.
It doesn't look like the broken chronology is having any severe negative impact on the topic. My recommendation would be to leave it as-is (maybe include a note somewhere about the chronology glitch) or start a new topic with the previous comments summarised.