Being from EU I chose to try the EU server (works nice, before I had a bit of a wait sometimes on the main server) but I noticed that if you close the renshuu tab and open it again, it goes back to the main server setting. I can still connect to the EU server by manually prefixing the address with eu (eu.renshuu.org), but that kinda makes the whole settings switch pointless. Of course it's not a big issue for me, I just have a feeling it's not how it's supposed to work
This is expected at the moment - it's not a fully integrated system, as I am still working to see how useful the new server actually is (I'm happy to see that it's working, though!). If and most likely when I set this as a permanent feature, this will definitely work in the way that you're expecting.