For replies to be an alternative to quote-posts, there need to be two things:
1. Better defaults across the ecosystem to make replies unlisted by default, so the home feed is mostly top-level posts—plus user buy-in w/this behavior (which would mostly come by changing client defaults).
2. Better presentation of PUBLIC replies to public posts, e.g. make them appear in the feed attached to the original post.
Otherwise, people are going to reinvent quotes with links like they are already.