Message 108431 - Python tracker
Sorry, I have no idea where that issue number came from. The correct issue is #812089. I just retested, and despite -remote being currently undocumented, it works on my windows VM with a current (3.6) version of firefox, and that the actions (eg: new-window) work as well. I don't currently have an OS X machine to test on, although that may change this week.