But again, this isn't going to be the case among people who know each other well. My family and I are interrupters, and we've been at it for decades now - none of the issues you're raising would apply.
In terms of knowing when/whether you can interrupt the interrupter/counter-interrupt/etc., see my other post in this thread about how the time of interrupters talking over each other is a signal to both that's constantly evolving (because the increasing time is an increasingly strong signal).
For certain. I'm less arguing that it isn't a conversation style, than I am that it is a dangerous one. Even in families, it is easy to see this form lead to resentment between folks. Or a contest to be last person talking. In a large sense, mansplaining is similar. Echoing back and explaining things even to people that know them isn't, itself, bad. But it is very easy to portray in a negative light and should not be the assumed default.
Now, I fully grant that the largest poison in all of this is the transactional view of conversation. The interrupt style is still predicated on an open transaction that will eventually commit.
In terms of knowing when/whether you can interrupt the interrupter/counter-interrupt/etc., see my other post in this thread about how the time of interrupters talking over each other is a signal to both that's constantly evolving (because the increasing time is an increasingly strong signal).