It may be my imagination but I think I see some comments or answers appearing after I write something although at the time I don't recall seeing them. I am judging this by the post time reported. Of course, it may be my memory showing my age! ;-) Or, is it possibly a bug? Or, is it due to time zone differences? Just curious.
Sometimes it does happen (happens a lot to me when i answer on my phone actually), there are several reasons for this.
It can happen that you were writing a comment/answer simultaneously. Normally you get a notification of updates.
The user may have deleted the answer, and that answer then becomes un-deleted. It will still get the original author time stamp stamp of when it was first posted seemingly appearing from thin air.