Tak jsem asi objevil příčinu proč to nejde :-(
Hi!
The term SFTP is a little bit confusing since it doesn't have anything to do with FTP. Instead, SFTP is a file transfer protocol on top of SSH and this is the problem here. By using the "sftp" program, you are *not* connecting to vsFTPd, but to the OpenSSH server, which does not have any chroot limits.
So if you really want to use SFTP, you have to set up something like "rssh" or "libpam-chroot", which is not trivial though. But your vsFTPd server supports FTP over SSL (FTPS), which should already work the way you want it to. So it might be easier to disable SFTP in /etc/ssh/sshd_config (comment out "Subsystem sftp ...") and use FTPS instead. You can test that with the "lftp" or "ftp-ssl" packages from the command line, or with the graphical "filezilla". Unfortunately, Nautilus doesn't seem to support FTPS.