There's probably a good reason why it hasn't been implemented yet. It's unclear what the reasons are, but something has probably got the attention of theymos. Although, a very neat addition to the forum I wouldn't class it as high priority. Hopefully, we see some higher threshold reporting badges now that there's several users on the forum with 30k+ reports. I'd like a very high one just to encourage users to continue reports as I feel 5k reports is easy to get within a very small amount of time. At least if we had say a 100k one it would potentially spur users on to keep reporting.
Theymos responded in that thread earlier on this year, but I think many people missed his post:
still waiting for it 
Sorry for the wait, when I went to implement this it ended up being quite a bit more of a can of worms than I originally thought because of opting out, preventing certain report-count-padding strategies, etc. It's still on my to-do list, but there are several things above it.
Is a report of a bump post in a long-forgotten thread worth as much as a report of someone luring Newbies into downloading malware in self-moderated topics?