I've observed that there's two sides of the argument here. Either, users here preemptively assume signature campaigners are posting just because they earn, when that isn't true for all cases. Besides, I've said this numerous times, I don't personally care their motive for posting, as long as it's of decent quality.
I was also a little worried since I once already reported a scam spammer and it now says '100% report accuracy', but I'm not sure if it's bad to have a low accuracy or not.
Unless, you're abusing the report feature your accuracy should never be the difference of you reporting the post or not. We appreciate all reports, it gives us something to do, and in the majority of the cases the report is handled good. Honestly, the majority of users are pretty accurate at reporting, however it's not a big deal if you get a few bad reports. I have over 200 bad reports for instance.
I partly wish the percentage was removed, and only good, and bad reports were displayed. Sure, users could still work out their percentage manually, but if it's not right there in front of them they'll likely not care as much.