It is possible, in two different ways, as long as you have a fixed set of sub-pages you want to fetch comments from.
If you have a large amount of sub-pages, or a variable amount, then you don't have a good scalable solution - and many have been looking for one:
For a Fixed set of sub-pages in your website, you can either use a batch request, or an FQL query.
Batch Request
First, you need your access token. Just enter the following as a url in a browser (credit to this website ):
https://graph.facebook.com/oauth/access_token?type=client_cred&client_id=APP_ID&client_secret=APP_SECRET
And this is the javascript jquery code to make a batch request to fetch comments from several urls at once:
$.ajax({
url: 'https://graph.facebook.com/',
type : "POST",
data: {
access_token : 'YOUR_APP_ACCESS_TOKEN',
batch : '[ \
{"method":"GET","relative_url":"URL1"}, \
{"method":"GET","relative_url":"URL2"} \
]'
},
success: function(data) {
jdata = JSON.parse(data);
$.each(jdata, function(index,value){
jdata[index].body = JSON.parse(value.body);
console.log(value.body);
});
// Do whatever you want with jdata
}
});
FQL
inspired from this post
FB.api({
method: 'fql.query',
query: 'select text from comment where object_id in (select comments_fbid from link_stat where url="URL1" or url="URL2")'
}, function(response) {
// Do something with results
});
Conclusion
Because of this limitation of Facebook, I plan to switch to disqus.com, which apparently supports this feature (As you can see from this blog, for example. (search for 'recent comments')