it seems you got it right! I don't know if you read email I sent you before posting to the mailing list, but I accidentally diagnosed the cause... :) I've noticed that inodes fsck warned me about, at least ones that I checked, all have all four timestamps latest in 2010...
The filesystem has maximum 1281998848 inodes, which is timestamp in august 2010. I don't know how it got that big, I think I did not specified big value initially. But I've resized it couple of times. BTW what is default of group size / inode count ratio? Mine ratio is not at the maximum you mentioned, but it is not that far.
So almost sure it is false positive by the code / bug in e2fsck/pass1.c around line 1070 in current version. I want to be sure that all these errors were caused by this, so can you please send me promptly patched version? I can easily patch it myself by some fixed condition, but I don't want miss something important... BTW maybe you can compare i_dtime with filesystem creation timestamp, so you dont have to put fixed number there.
BTW I dont know specifics of ext3, I just looked at sources of kernel driver and e2fsprogs now. But what indicates that inode is / was created and valid ? (I did not need it to find problematic test you mentioned, did not see it in part of code I look at and it is not apparent to me from definition of struct ext3_inode).