Both Windows and Linux should execute that extension correctly.
Windows executes the extension correctly, but Linux received syntax errors.
Windows 10 using Brackets 1.8 (latest as of 2/11/17).
Ubuntu 16.04 using Brackets 1.8 (latest as of 2/11/17).
getting rid of es6 in UI portion of the extension
this is sadly a long running issue of the Linux version going out of date due to the difficulty of integrating/keeping up with CEF releases on the Linux version. The Brackets-Electron version that we now usually recommend to install over the CEF Linux version has vastly better support for ES2015 features AFAIK, but I understand that this might not be a solution for an extension.
Note to self: Might be worth adding that issue to the Linux Guide too: https://github.com/adobe/brackets/wiki/Brackets-Linux-Guide.
Thanks for the info, that's good to know. I already updated my code, so that's not a big deal. But it is good to know that I will need to test against Brackets-Electron, since that is officially recommended in the docs.