> then surely you can handle replies in a tree view to show quotes in a firehose
One problem is that when people are manually quoting a post, they can edit that quote down to only include the relevant portion of the post they're replying to, and depending on the forum culture unnecessary full-quoting is actively being discouraged.
Automatically added quotes on the other hand don't have such a luxury, so you'd get a big bunch of full quotes, which wouldn't really be ideal, either.