Is setting the pretokenise flag advisable?

Does the code processed by eval get pretokenised, provided the flag is set?

It does, yes :) If you were to manually install the command-line tools from https://github.com/espruino/EspruinoTools then do espruino --board ESPRUINOWIFI --config PRETOKENISE=true foo.js -o out.js then you could actually get the code tokenised in a file, which you could serve up over TCP if you wanted :)