Hi
We can do it.
Please have a look at this old Forum post:-
Link:- http://help-forums.adobe.com/content/adobeforums/en/experience-manager-forum/adobe-experience-manage...
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1. Offcourse it is possible. I recommend not to delete atleast any of [1] to be in par with documentation. Deleting group does not remove acl.
[1] http://www.aemstuff.com/#article959
2. It's not recommend to delete built-in groups with the system if you want to use samples on author. The sample apps use these groups. But if you are not interested in ever using the CQ sample apps to learn, etc, then I suppose you can delete them. But leaving them on author does not impact CQ performance or other detrimental side effects.
I hope this would help you.
Thanks and Regards
Kautuk Sahni
Kautuk Sahni