[nasso_dev]

Displaying comments is cheap because the AppView (the "cache" layer that consumes the aggregated feed of records from the relay) can maintain a relational database of the social web/graph.

When it receives a post, it creates a row in the Post table. When it receives a comment, it creates a row in the Comment table, which has a column pointing to the Post it's replying to. Then, getting all comments under a post is easy SQL.

About your second question: yes, you're correct. What handle you use and where your data is hosted are completely separate matters.