It is not possible to set sticky bits via sftp due to the following code in the process_setstat() function in sftp-server.c if (a->flags & SSH2_FILEXFER_ATTR_PERMISSIONS) { ret = chmod(name, a->perm & 0777); if (ret == -1) status = errno_to_portable(errno); } If the user has shell access then they can execute a chmod command via ssh to get round this therefore even if there is a security reason for doing this it should at least be configurable. If there is a valid security reason for doing this it should be noted in the FAQ. I found this while attempting to use sshfs, which uses sftp underneath.
*** This bug has been marked as a duplicate of bug 1310 ***
Close resolved bugs after release.