Our SFTP server provides "." and ".." elements primarily because most third-party servers including OpenSSH (the most common SFTP/SSH server) provide them as well.
Due to this being a common behavior, any SFTP client app that does not wish to process these elements should simply skip them (which is what our SFTP client actually does). I guess doing the same with Renci would be quite straightforward as well. As a bonus, this client-side solution would work with third-party SFTP servers as well.
If this is not practical for some reason (for example if the client application cannot be easily modified), we would consider adding an option to Rebex File Server that would disable providing "." and ".." elements to SFTP clients. In this case, please contact us at firstname.lastname@example.org if you are interested in this solution.