The rather constrained character limit is one of those endearing appeals when it comes to Twitter, but to be able to introduce some sort of commentary to a Tweet that you already intended to share proved to be close to impossible in many a case, and hence, it became a stumbling block when it comes to sharing and communication.
All of that is no more, although the new functionality will not be available on third-party clients, which makes it a wee bit odd. It remains to be seen whether third parties will eventually adopt the new functionality, since Twitter always wants to drive users to the native apps. Do check out the latest update on Google Play if you are interested.