I've been experimenting with this module and filecache on a Acquia Dev Desktop, and am having some problems with new comments being shown in both 7.x-1.2 and 7.x-2.x-dev.
With both versions, new comments do not show up on the node page when you refresh the page after adding a comment, or navigate away and come back. However, the comment count in the view on the front page is updated, and you can see the new comment before you refresh the page. It is very similar to http://drupal.org/node/1881998, but the patch identified there has been implemented.
In 7.x-1.2, a number of warnings in pairs were generated in the log:
Warning: array_map() [function.array-map]: Argument #2 should be an array in _authcache_comment_num_new() (line 155 of C:\Users\gurrma\Sites\acquia-drupal\sites\all\modules\authcache\ajax\authcache.php).
Warning: array_combine() expects parameter 1 to be array, string given in _authcache_comment_num_new() (line 157 of C:\Users\gurrma\Sites\acquia-drupal\sites\all\modules\authcache\ajax\authcache.php).
But nothing on 7.x-2.x-dev. In Authcache debug, the ajax request for the comment form seems to be the same on the page where you can see new comments immediately after adding them, and when refreshing that page.
Can anyone shed any light on this? Thanks...