Pepijn, why "without having to edit their original post"? Just add "edit: I meant this not that" at the end of it. Mastodon in particular stores and shows edit history for posts so "he edited it after the fact to change meaning" is not as much of a concern.
@grishka @renchap Multiple reasons. The ones I see:
-it might not be the only time a post is quoted. Quoting a post is starting a conversation, being able to reply makes it a fairer dialogue.
-character limits: there's not always enough space.
-that's simply not elegant, it's confusing in the original feed and all other places where people have no idea about the quote post. It makes the experience for everyone not reading the quote post worse.