In my opinion, most people won't get confused by the 'old' interface being at a different subdomain, especially as Reddit did it themselves (apparently they had new.reddit.com which hosted an older redesign than reddit.com, like wtf!?? But somehow people understood that distinction, so this should be fine) Then again, I could be too much of a nerd and overestimating people :P (insert relevent xkcd here)

btw, does sopuli.xyz have the mlmym interface?