Language on JFBCComments

That's a great question, and something we haven't tested. However, we had looked into it at one point, and the page below is what we found:
forum.developers.facebook.net/viewtopic.php?id=29112
Specifically:
Q: How does the Comments Box work in other languages?
A: Because of Facebook's user-provided translations application, the Comments Box UI will automatically display in a user's chosen language

Again, we haven't tested that, but it is from an administrator on the Facebook Developer forums. Unfortunately, it's also a pretty old post, so may be out of date. Please try with a Facebook account who's default is Danish (or your language of choosing). This can be set in Facebook by going to your "My Account" page and then using the language tab.

I don't know of a way to 'force' the comments block to always be in a specific language.

Yes, you're correct. We actually stumbled across this over the weekend and remembered your post. Currently, and somewhat unknowingly, we've hard-coded the language into the Javascript. We'll make this a configuration setting in an upcoming version. For now, if you'd like to set it yourself, please do the following:

Edit the /components/com_jfbconnect/libraries/facebook.php file. At ~line 75, update the line below with your country code:
<script src="//connect.facebook.net/en_US/all.js"></script>\n

When we do a setting in the future, we'll likely make it a global configuration setting (or pull from Joomla's default language setting). If you have a preference or suggestion on how you'd like it done, please let us know!

Thanks for following up and making us track this down.

Awesome. Yes, we would like to do something like that (so it's automatic). There's also a way to pull the user's langauge from Facebook itself, but sometimes that requires the user to have already approved your app.. which is poor.

Either way, we're investigating. Won't be in the next release (due soon), but short after.

Thanks for providing your code. Looks clean and easy.. now to make it work for all languages easily

Yes, we'll be making the language selection flexible (or automatic) based on your Joomla settings. Haven't decided the exact approach yet. Again, it should be in the release after 3.0 stable (do this week).