Created by: marcofugaro
Snooping around UglifyJS docs I discovered that as of version v2.8.5, the version which webpack uses, the option screw_ie8 is enabled by default:
--screw-ie8
Use this flag if you don't wish to support Internet Explorer 6/7/8. By default UglifyJS will not try to be IE-proof.
That might look a bit vague, but looking in the code I found the default values, screw_ie8 defaults to true and output.comments defaults to false
https://github.com/mishoo/UglifyJS2/blob/e5cb9275df257751b7322f34bca5e76cc519b974/lib/output.js#L81
https://github.com/mishoo/UglifyJS2/blob/e5cb9275df257751b7322f34bca5e76cc519b974/lib/output.js#L78
The commit I'm browsing in is the v2.8.5 one https://github.com/mishoo/UglifyJS2/commit/e5cb9275df257751b7322f34bca5e76cc519b974