Do you mean itmejp.com or community.itmejp.com?
I've not looked into it but I would put money on itmejp.com using a plugin / pulling from the api for the community site which is handling the timing differently to the timing on the main community site.
If people really want down to the min timing on activity I will look into it when I'm up and running again with a workable dev machine. (Trying to work on my current set up is painful, so I'm trying to hold off until I get my main machine running again).
Personally it doesn't bother me once it hits the rounding as when I'm interested in replies I use the notification system or the difference in title colouring to alert me to new posts.
I'll have a look and give you a more definitive answer as to X does one thing and Y does another when I get to my desk.