Quite a few blogs have a section in the right sidebar on the front page which links to the most recent comments, typically citing them by each commenter's name and the title of the post they commented on.
When I comment on other people's blogs, I usually return directly to the comments section under an article if I wish to find out whether anyone has replied to my comment. If they replied more than a certain number of comments ago their comment won't be referenced on the front page anyway.
A cynic would say that the utility of the front-page latest comments section lies mostly in allowing a commenter to feel happy at seeing their name up in lights. But of course that may be exactly the effect that a blog writer seeks. It also kind of shouts out "We get lots of comments traffic, you know", as if the traffic level were an issue. And if say the latest five comments have all been on the same article, then its title will get shown five times, which doesn't look nice at all.
On the plus side, visitors can learn from the recent comments section that an old article, or one they haven't read, is attracting current interest, which might spur them to read it, or at least to read the latest comment on it.
How useful is this device and when?