A Unix file system is not only a map from paths to inodes to bytes. Unix file systems support a host of additional apis, some of which are hard to implement on top of something like s3 (eg atomically renaming a parent path).
Even if you drop the Unix (posix) part, most practically used file systems have features that are hard to guarantee in a distributed setting, and in either case simply don't exist in S3.
The point in my post was to point out that storage implemented using keys and values is fundamental to all filesystems. To say that the very model that is fundamental to all filesystem is the thing that somehow precludes S3 from being considered a filesystem is kind of bizarre.
Also Nowhere did I say or even imply that a key/value store is all a Unix file system is. Different filesystems have different features. Object storage is a type of filesystem with a very specific feature set.
I understood the original poster as saying a system providing only key/value storage is not the same as a file system. I'd think that's something we can all agree on?
Even if you drop the Unix (posix) part, most practically used file systems have features that are hard to guarantee in a distributed setting, and in either case simply don't exist in S3.