For the 5k ABP I believe it was locutusofborg, but it could be SingleSS. When I am posting this they are the only two above 5k ABP. locutus has around 6k and Single around 5k. I'll check grepostats to see who got it first. I'm too lazy for screenshots. elchivo78 is first to 10k total BP
Edit: locutus was first to 5k ABP according to grepostats, achieved on 12-10-12.