Sorry if you've had the wrong impression on some things. Up until earlier this month, JFBConnect has supported responsive comments. If you check the following file:
components/com_jfbconnect/assets/jfbconnect.css
That has the line from the Stack Overflow post you referenced:
.fb-comments, .fb-comments iframe[style] {width: 100% !important;}There's actually additional styles in there to improve the responsive comments in Joomla in general, since that CSS didn't fit every template's needs, we found out through testing and bug reports.
That file should be loaded whenever the Facebook Comments are loaded on your page. If not, there's something else going on.
With that said though, Facebook recently 'broke' the ability to override their styles since they embedded the width within the iFrame'd code itself. Due to cross-scripting permissions issues, it's simply not possible to override CSS within an iFrame. There is a long bug report about this issue that was started earlier this month because of this change on Facebook's behalf:
developers.facebook.com/bugs/256568534516879/
We're definitely following that report to see how they correct the issue. If there's anything else we need to implement once it's 'fixed' by them, we definitely will.
For now, unfortunately, it's not possible to make the comments responsive.. that we know of. If you've implemented those styles and had luck, please point us to a page they work on and we'll gladly investigate further. We've done a lot of testing with the change FB made earlier this month and didn't have any luck.
I hope that helps explain, but should you have any other questions or suggestions, just let us know!
Thanks,
Alex