The bug here is that we only added a state_change value if the old state differs from the new state. That means that the third comment should actually look identical to the second comment.
Like this:
That's how it worked in XF1 too and it now works the same in XF2.
I think, longer term, it might be nice to also show who the report was assigned to. We could do that a few ways. The easiest might be to just populate the "message" field of the comment... but that's a bit yuck. We'll call this fixed for now.