PhilK:
I disagree on this. I make a point of replying to all comments, pro or con. (99% of them are pro, luckily.) It seems to me no more than courteous, and after all how long does it take? If it's really taking you a week, Seb, you must be the most commented author in the Library - or maybe the slowest writer....
Since I am not an author, I have no reply comments. I still feel that I do not find it necessary to reply on all comments by me, especially so, if I comment quite a bit for one author. I have commented on each part of a very large series. The author still does not have to reply on each of my comments. If course, if they find something interesting that I commented on, then they reply.