This new facility on twitter has taken a long time to arrive, with the facility being on third party apps for a long while.

Good to see it's finally being rolled out, on twitter.com for the moment, and to mobile later.

Conversations surrounding a Tweet, particularly if they’ve sparked lots of replies and disparate conversations, can be hard to follow. So, we’re doing a few things to make this much easier: grouping conversations together and highlighting some of the most interesting exchanges surrounding a given Tweet right below that Tweet. To surface some of the most interesting conversations, we’ll take factors into account like whether the original account has replied. Twitter Now Makes Conversations Easier To Follow [blog.twitter.com]