What factors determine when it’s good UX to nest comments on a blog?

Nested comments in the sense of comments that are progressively indented according to their level in the hierarchy are an abomination according to my personal taste, because I tend only to participate in blog comments sections where commenters can keep track, at least most of the time, of who is commenting on what point made by whom - and who write so as to make it easy for their readers to do the same, if necessary using the ">" character or italics. Help to keep track in the form of indentation would make comprehension more difficult, not easier. The effect would be similar to the irritation that is felt when you are understanding perfectly what another person is saying and yet they keep asking "Do you know what I'm saying?" But that's just me. I'm not a typical blog commenter. So my question is this: what factors have been reliably determined to govern when nesting comments assists or hinders UX?

I have in mind variables such as

• the number and spread of comments and commenters per article
• a user's typical level of education and their skill at expressing themselves in writing
• the heatedness or otherwise of the interactions among commenters
• restrictions on the depth of nesting
• implementation of indentation, for example with or without vertical lines on the left hand side.