How to encode comments in a hierarchical manner?

Many blog platforms allow to post a comment as a response to another
comment. Is there a way to encode the hierarchy of responses in RSS?
From what I can see RSS2 only has <comments> element that points to a
page with comments. But it seems to be useful to have a <comment>
element with the ability to include another <comment> element within a
comment element, or to be able to include a reference to the parent
<comment> element.


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