This is just stupid, in my view. What's the point of a supposedly open platform if only a select group can respond to things said? A "conversation" on twitter can be just like a thread on a messageboard, where the members are clearly defined: people you follow or the people mentioned in the tweet. Amyone can still see the tweet--just like anyone can read threads on most messageboards--but only the members can participate.
But you know, I both agree and disagree with the last. As awful as twitter generally is, there some bright spots, some actual realtime exchanges of important info, of critiques, of observations, and so forth. If we could only find a way to remove all of the assholes (and there are a lot of them). 'Course, that's true of the internet in general, as well. And life.
As to this change reducing nasty comments, that's no doubt true. But again, it makes twitter into just a series of (temporary) messageboards.
Seriously, part of me wants to grab a lot of these people upset over the nasty comments and shake them violently. It's like they all just discovered there are mean people on the internet, completely unaware that this has been going on since day one. Sure, the scale is ridiculous now, but most of the people on twitter, on the internet, don't need to be there (I include myself).