That's a "web issue", for instance personally I follow HN via feeds, sometimes with nnhackernews (Emacs/Gnus backend) witch makes seen edits difficult. In class

That's a "web issue", for instance personally I follow HN via feeds, sometimes with nnhackernews (Emacs/Gnus backend) witch makes seen edits difficult. In classic discussion system (like Usenet) to ease read there is no edit, just a timeline. Also edit potentially "vary" posts leaving old answers untouched underneath making the conversation potentially hard to read for someone coming late.