It's for more granular access permissions for files and folders.

Yeah, but I think all reasonably-modern Unixy filesystems on Linux will support ACLs. ext2/3/4, btrfs, xfs, zfs, jfs, etc.

Yes. Some filesystems straight up do not support ACL of any kind (eg: fat32)

I don't really think that that's a realistic goal for ACLs. I mean, getfacl showing the user specifically being excluded probably isn't any more-polite.

In a previous life (in the 90s) I was a un*x sysadmin, and ACL is nightmarish in big company, I hated it and avoided it

Whoaa, are you ACLing sober? Slow down champ!!

I think it's like this: what used to be group in regular permissions output is a union of group and ACL mask in ACL output. Mask sets the upper limit of what ACL can do, so if mask is rw- then it's impossible to set a r-x ACL permission because allowing execution is not allowed.

This seems to be more geared towards enterprise environment where it could be complicated to cleanly define groups, since you can only give access to one you might run into a problem where dept. A needs access to that directory but also person G from dept. B and person K from dept. C.

I mean in this case it's to show what ACL means, not like RIP in peace

Permissions are listed as "user", "group", "other". I.e. the user who made the file, the group of the user who made the file (usually just their name as a group), and everyone else. In this case the rxw is for the user.

For chmod, you can also represent these as binary numbers: 111 would mean having all 3, 101 would mean having read and write, etc. These binary numbers then get turned back into regular numbers (7 in the first example, since it's 111) for chmod. Giving a file "chmod 777" means the user, group, and other all have full permissions on the file. "chmod 700" gives the creator full control, but no one else can view, modify, or execute the file.

Read, extend, whitelisted

it’s a really awesome website

I've been a network engineer for five years at three companies and not a one has used switch or router based ACL's. It's all in the FW appliance.