At the time of posting this, I have a reputation of -1.

If I knew which of my posts had a negative reputation, I would be able to get feedback and perhaps modify my behaviour so that other members would be happier with my post content.

Similarly, for others' posts where I cannot vote, it would be good to see reputation, so I can analyse what makes a 'good' post.

However, I can ONLY see post reputation on posts where I can vote.

Yeah, don't know why it's not like that already. If you can't rep a person you should still be able to see that post's reputation level.

Just noticed, it's a bug, reported in the tracker, and accepted.

Yeah, not being able to view rep points on a post you can't vote on is a bug. As to viewing which of your posts have been rep'd, that's probably a good idea, something we can keep in mind for a future version.