I remember seeing this feature implemented on paid-subscription Twitter accounts. Personally, I simply auto-blocked anyone who did this.
So, while I understand the desire for this feature, and have no particular objection to it, I want the ability to keep my own timeline free from anyone who simply wants to indulge in monologues.
For me, the sadder aspect of this is that it is a band-aid to avoid grappling with a deeper rooted issue - a failure to conduct respectful discourse.