Opening a file stored in HDFS to edit in VI
There are couple of options that you could try, which allows you to mount HDFS to your local machine and then you could use your local system commands like cp, rm, cat, mv, mkdir, rmdir, more, etc. But neither of them supports random write operations but supports append operations.
NFS Gateway uses NFS V3 and support appending to file but could not perform random write operations.
And regarding your comment on hue, maybe Hue is downloading the file to a local buffer and after editing it might be replacing the original file in HDFS.