I read that FAQ but none of it applies to me that I can see. I have installed many many extensions to this site with no issue so I know the folders are all proper and permissions are set properly. Your FAQ says "Check if you have installed a plugin named 'System - MightySites' and in such case unpublish it temporary before installing the component." I was already positive I did not have that plugin installed but checked anyway and no, I do not have it.

Kinda hard to claim the issue is solved until the extension is actually installed wouldn't you think!