Multiple comment structure / feedback

Hi there,
is there a function to enable something like a multiple comment structure, so that comments can be commented. Sort of like at yahoo list.
I imagine it like this:

1. posting
1.1. comment 1
1.1.1 sub-comment 1.1
1.1.2. sub-comment 1.2.
1.1.2.1. sub-sub-comment 1.2.1.
1.2. comment 2
1.2.1. sub-comment 2.1
…

I hope you understand what I mean!

Many thanks in advance…