What you see on Jury service is the original post (OP) of the thread at the top, and the questionable post at the bottom. In between are direct replies between the OP and the questionable post (if there are any).
If the questionable post is a direct reply to the OP, you'll just see those two posts. Here's an example where the questionable post is the fifth reply in the thread, and it's a direct reply to the OP:
OP
--- Reply 5
On a Jury, that would be all you see, because the 5th reply is directly replying to the OP, so that's all that's needed.
But if there are other posts in between the OP and the questionable post, you'll see all of those posts so that you can see the direct chain of conversation. What you won't see are posts which may come above the questionable post, but don't have anything to do with it.
In the following example, Reply 8 is the questionable post, which is a reply to Reply 7, which is a reply to Reply 4, which is a reply to the OP. I've italicized the posts which are not in the direct chain of conversation:
OP
--- Reply 1
--- Reply 2
--- Reply 3
--- Reply 4
------- Reply 7
----------- Reply 8
--- Reply 5
--- Reply 6
So when serving on the Jury, you just see the OP, Reply 4, Reply 7, and Reply 8.
We decided to do it this way because lets say you have a 50-reply thread where the questionable post is the 49th reply, and it's just a direct reply to the OP calling them a name. If you're on a Jury, you definitely don't need to see the 48 replies that come before the questionable post -- in fact, they would be very distracting and people might get put off if they had to scroll through all of them.
So instead we opted for a system where you only see the direct chain of replies that links the questionable reply to the OP. That is a record of the complete conversation between the OP and the questionable post, and it should be all the information you need to make a decision when serving on a Jury.
Hope that makes sense