*caugh caugh*
Sorry for bringing up this topic from the dead, but here's the biggest evidence i can find for this topic, although it's in the reverse direction.

Here's my theory on how it works:
It's the path in which the send/receive signal takes that are different, resulting in different pings.
I do tests on certain servers in which a volunteering dretch strafes side to side, and i lock onto him with my mouse, using a lasgun. I fire slowly, and if it doesn't hit, i adjust forwards/backwards until it hits. I then estimate the ms/distance i aim ahead/behind the dretch and this follows up:
For US official, i have to aim
back about a maximum of 40 units [~100 ms, or one whole dretch and a bit behind] againts dretches.
On Fg* Server, i have to aim
ahead about a maximum of 60 units [~150 ms, or two whole dretches ahead] againts dretches.
On Asia unofficials
witout unlagged on[i usually don't use unlagged there for humans] i have to aim ahead ~40 units [mathematically speaking, its almost exactly 44.8 units] from a constant ping of 98 (sometimes goes up to 200 randomly) againts dretches. Lagged seems more reliable for me on this server.
Anyway an example of the path theory, since i live in australia connecting to an american server, the 'send' would be travelling under the pacific ocean which results in me sending the signal early , while the receive signal could be travelling through Japan, which results in me receiving the signal late.
Each side can only predict the ping by averaging the two signal speeds together which means my lower ping could be as low as the eastern australians [~250] if the signals take the shortest path.
