I had to feed it the hex codes as the shell didn't like those characters. I also had to replace the space with the invisible character:
# nvram set wl_ssid=$(echo -e 'xe2x94x93xe2x94x8fxe2x81xa3xe5x87xb5xe2x95xb1xe2x8axbfxe2x94x8cxe2x94xacxe2x94x90x0a')
# nvram get wl_ssid
┓┏凵╱⊿┌┬┐