And you are running 10.13.1? And all you did was go into the editor and click the quote button once?
Yes, I am on OS 10.13.1 (High Sierra), Safari 11.0.1, and Chrome 62.0.3202.94.
However, clicking on the quote icon
for the second time will result in a quote inside a quote:
[quote ][quote ] [/quote ][/quote ] (once again, spaces inserted deliberately by me)