[dhx]

It is easier for a user to scroll down a long continuous list than to hop back and forth between two columns. This is particularly true for ordered lists (as is the case with HN).

The only thing I strongly dislike about HN's current design is that comment line lengths are far too long[1].

[1] http://baymard.com/blog/line-length-readability

[XLcommerce]

It reads like a newspaper. You read one column at a time. No hopping between columns.