Presentation of generated images for i18n content for AUTHENTICATED users has gzip header (they fail) - anon presentation works

OK, given...

• php.ini has "output_handler = ob_gzhandler" configured.
• I have i18n content and alternate languages as part of my site.

What happens is...

• ImageCache in all cases generates its images to the file system properly.
• Anon site visitors see ImageCache generated images fine for all language cases - server to browser transport works as expected.
• AUTHENTICATED users CAN see native language image content fine. Example path:
  http://example.com/sites/default/files/imagecache/hero-img/myproduct-en.jpg
• AUTHENTICATED users CANNOT see alternate language image content - http content header "Content-Encoding: gzip" is in effect for mime content image/jpeg which makes no sense and generates a "Error 330 (net::ERR_CONTENT_DECODING_FAILED)" in Chrome. Example path:
  http://example.com/de/sites/default/files/imagecache/hero-img/myproduct-...
• Commenting out "#output_handler = ob_gzhandler" in php.ini makes all of this go away. But that's a bit extreme (right?)

Questions...

• Is this bug? Or is php.ini "output_handler = ob_gzhandler" simply "not recommended, have Drupal manage compression instead".
• Even if it's a bug, why is there a difference in data transport between native language paths and alternate language paths for authenticated users vs. anon site visitors?