For those readers who wonder what this thread was all about and want to verify some of the claims that were made, I have created a demo file with part of the text used by the OP. I also attach a better readable screenshot which hopefully makes clear that the "gibberish" contains valuable information, namely the hex value of the character that can't be interpreted by the reading application.
When removing the fake gz extension and allowing Abiword or Geany to open the file with automatic encoding detection, 3 of the characters will appear as blocks with a number in it. I briefly checked with other applications and can confirm that Leafpad can read the file correctly. Worse than Abiword and Geany were the commandline editors e3 and mp who would either skip the three problematic characters or replace them with useless ASCII characters like ~V.
Worst of all was LibreOffice 4.3.0.4. Unlike all other applications LibreOffice Writer failed with the international characters in the demo file. I couldn't even find an option to select an encoding. Maybe a newer version works better.
The demo file also contains some explanations why I claim that the screenshot presented by the OP is a WINDOWS encoded file and can not be an ISO or IBM file.