If you add Facebook comments to your page and you see Array in the place of where the comments should be - please read below:
In many cases where we have seen this issue we've found it to be down to either the Facebook APP Id not being entered in the dashboard field, or the APP not being setup correctly. If you run your page through the Facebook debugger you will see what issues there are (note your page will need to be published in order to do this):
Facebook debugger link: https://developers.facebook.com/tools/debug
You should follow the guide below for setting up your Facebook Comments APP ID:
Other Potential Causes
To correct this go to pages, find the page in question and click on edit. Then look to the top right of your screen for the tab that says; 'Screen Options'
From the drop down click the Discussion box.
Then click the Wordpress tab (beside the OptimizePress tab) that are both under 'Edit Page'. Tick the 'Allow comments box.
Click the publish "Update" button in the right column then reload your published page and your comments should now be working correctly.
Your comments should now be working correctly on your published page