Hello David, Toby. I am inclined to agree with you both on most points, particularly the in-reply-to thread extension. But I would like to quietly remind you both that the subject is a "comment" (singular) how to nest, group a comments is not a topic of this conversation. That said I am not saying we should not be aware of grouping, just that it is not explicitly part of this problem, Its the simpler problem of "a comment". I have updated a comment schema 1 [1] to try and reflect the points highlighted in this conversation. [1] http://microformats.org/wiki/comment-brainstorming#Schema_I Best wishes -- Martin McEvoy http://weborganics.co.uk/