The above image is just one of my latest bad reporting. As I have said on my previous reply
I know moderators don't have the time to read all the previous post, but, if there will be some ratings on the quality reporters I would have the lowest ratings just because I forgot or never link which post I was saying as rehash post.
I also have one report which got a bad report, AFAIK the post was just

(yup, just a smiley and got bad on that), when I check again it was already deleted. I know moderators can see this link, if I'm correct it is just a smiley >>>
https://bitcointalk.org/index.php?topic=5134505.msg50705307#msg50705307My bad reports are around 0.81% of my total reported posts. I hope it won't affect my quality of reporting, I know we all make mistakes or moderators click the wrong button and I admit I make mistakes.
It really depends on if you care about report percentage, and actually removing the message. I'm only speaking of my viewpoint on this, and how I go about moderating. I'll try my best to go through the pages, and check if there's duplicate content, but if I believe that the post is unique enough or adds just enough to discussion then I'll likely leave it. Sometimes I'll ignore the report, and possibly allow another moderator to make the decision if I think its borderline.
My point being without going off topic too much here is that if you report with references its much better, although its not a requirement, and most of the time its not needed. Regular reporters, and moderators can kind of spot duplicate content from a mile off due to the fact that we get reports, and report within the same threads quite a lot.
If its a smiley then yeah it should have been deleted, and I'm not sure why it wasn't marked good, but it was probably just a mistake on the mods behalf. 0.81% is a really good margin for error, I wouldn't be bothered by making too many mistakes guys, and as long as you have a good amount of good reports then there's no real need to change from a personal perspective. Back in my reporting days I made over 200 bad reports.
My personal advice would be to go more in depth on non obvious cases. However, simply stating "spam" etc is usually fine for the majority of low quality content. I fully agree with your post especially with the part in bold. If a reward system like that got implemented I think that not everyone should be able to participate in it. It should be based on the stats of good reports, both quality and quantity wise. That way you would be dealing with a handful of members who already know what an off topic and spam post looks like. That minimises the possibility of abuse and gaming the system.
But, people get greedy, and will game the system by creating alt accounts, and posting spam, and reporting it with their mains. Then, the original goal of the campaign of removing spam is void, and we are left dealing with more spam than original. It's a hard one, but the very core of the idea is a good one.