I think I have probably been ignoring comments and emails for months. You see, the Gmail address that I use for this LJ (as well as for Facebook and ff.net) is just a forwarding address, that sends everything on to my "real" email account. I paid a very belated visit to my Gmail inbox today to do some deleting, and found it scattered with "mail delivery failed" messages, all relating to the forwarding of LJ comments. My Facebook comments and ff.net notifcations are still being forwarded properly, but my LJ comments are all being rejected and are thus never reaching me. So apologies if anyone has left comments in the last few months and not received a reply. I'll try to remember to check my Gmail inbox more frequently in future.
EDIT: But not yet, since I'll be away over the New Year, so won't be able to reply to anything for a few days, even if I do receive it.