I agree, it’s annoying to follow a topic with multiple short replies in sequence.
But there are legitimate use cases for this. Say I wanted to post something like a live blog from the new ipad launch in a discourse forum. Should I write one post and edit that 100 times to add content or add 100 replies in sequence? The first option would be much easier to read after the event, but anyone following live would have to be constantly refreshing the page to see the edits. So I would naturally opt the latter strategy and add endless replies that get updated in my followers screens in real time.
As for posters just being lazy or ignorant of edit button and posting sequent replies, there are two options:
Maybe we could tweak the ui to show sequental posts from the same author with less metadata overhead? Just separate the posts content with thin horizontal lines for example. Completely disallowing sequental posts seems too radical to me.
a quick ui mockup of combining posts in ui:
