From Twitter’s quarterly earnings (PDF):
We are going to fix the broken windows and confusing parts, like the .@name syntax and @reply rules, that we know inhibit usage and drive people away.
Replies are limited to followers of both the sending and receiving accounts for a reason: ostensibly, only those users care about both voices. But there are lots of instances where a reply should be more public and go out to all of the followers of the sender account — hence, the dot-reply syntax. These rules are too complex for many new users to understand, but I’m interested in seeing how Twitter “fixes” them without junking up everyone’s timeline.