Hi, i got the same problem with my site. Because there is no language-adjustments in the options, i think it should work automatic, but it doesn't. Everything is in german on my site except the comment on front-end.
Changing the template didn't work either.
Any help? I'm using Joomla 1.7.
Guys please if you find that your language files are not loading enable system debug + language debug and go to your frontend/backend. At the bottom of the site you should see information about the loaded language files + language errors.
If you see errors in the language files for com_comment please repair them and send us updated versions of the files - I'll then include it in the next release.