Conversation

Replying to
People being too lazy to read through a thread before replying is pretty common. Twitter makes it worse by actively encouraging it, making it hard to browse threads and giving notifications for indirect replies, etc. by default. It's designed to maximize replies + notifications.
2
Replying to and
This and sometimes, the other replies don't load right away. Sometimes it'll look like there's no replies until you reply or refresh and only then do you see the seven others. Makes sense that it relies heavily on local cache.