Okay guys, we've had a few issues with the commenting system of late and a solution has been worked out. The issue was blogger has introduced a new setting in mobile themes which overrides custom commenting systems...gee thanks for telling us. protip - make your commenting system better!
Anyway, anytime anyone commented on a post through a mobile device, IntenseDebate was shut off and the old blogger commenting system was brought back online - hence posts starting with IntenseDebate and then losing all comments and reverting to old-school blogger commenting style.
I've hopefully fixed this by disabling the mobile interface until this issue is rectified - if it is. I don't know how this will affect mobile users so if you could please inform me, that'd be great (and also check to make sure the IntenseDebate commenting system is working now by commenting here!).
Anyway, sorry for the troubles. All the posts which now have blogger comments on them will stay that way unless I reset the code (which I'm not going to do) but all future posts from this time onwards should stick with the IntenseDebate system!
