Comment caching will only work with one of these options: “v1 only”, “new”, or “v1 and v2”.
This is because if you use the new v2 alone, the comments aren’t imported into the v1 system. Thus there’s no way (currently) to retrieve v2 comments via any api. And threaded replies aren’t counted no matter (which is the same behavior facebook themselves uses; but I don’t like it).
Also, you should change all get_option('fbComments_XX') to, $arr = get_option('fbComments'); and use $arr['XX']; when you need the value. Currently your code will still work (however if you change your xid it will still retrieve the old one), but in the future it will be removed, and using an array should be slightly faster (or a lot, if you’re calling something for every post).
