I went into my Statistics page today and found that chinese message in my "visitors Message" box. How it got in there I am not sure but there it was.
Very strange !
I removed it from there using the options listed and had to log in again to proceed with the removal of this message. First time I have done this so not sure if it was a ruse to obtain my password or not but nevertheless it's now gone.
I will update further if any of that kind of thing comes back.
The one-touch-ban option doesn't reach to Visitor Messages, but we can still do a manual ban and clean from the back end. It's a spammer most likely, but if you get the username we can take a closer look