Just for the record, as @hvelarde found, comments *are* removed:
* https://github.com/plone/Products.ResourceRegistries/blame/master/Products/ResourceRegistries/tools/packer.py

And we could also be happy with the fact that Plone's JS are delivered with no worries on that issue:
* https://github.com/plone/plone.app.jquerytools/blob/master/plone/app/jquerytools/browser/overlayhelpers.js
* https://github.com/plone/plone.app.jquerytools/blob/master/plone/app/jquerytools/browser/jquery.form.js