This bug has been introduced in january or february 2011 and is still not fixed.
Since I hate repeating myself:
I thought the new networking code would fix it once and for all, but I was dreaming again...
For some reason the FPS window didn't get captured, but I had around 5 FPS here while I normally should have 50-60.
This is a critical issue since not only it gives wrong positioning, "invisible" characters hitting you, etc.. (read the first topic), but also a huge FPS drop that even supracalculators and latest graphical cards can't cope.
This is just totally ruining the gameplay.
When the hell will you care of this very poisoning issue?