I’ll just quote the tl;dr here, pls visit the forum post linked above for in-depth information:
anoek wrote:tl;dr We're switching to a Glicko-2 rating system, which should be great for a lot of reasons. All of your past ranked games have been accounted for during this transition.
“The only difference between me and a madman is that I’m not mad.” — Salvador Dalí
We will see how good is the new OGS ranking system. One of the problem of OGS in the past was its ranking system, confusing 3 ranks, slow to adjust. Hopefully it will improve.