> If the connection breaks while an ACK is outstanding, the sender will have no way of knowing whether the segment was received

The real question is, why this should be a problem that TCP must solve? TCP gives you a bidirectional waterflow-like pipe, and that's enough for you to create many useful applications. TCP never provided guarantee for correct delivery, that's your job.

For example, if a HTTP request is interrupted before the respond is received, the sender should assume the request never reach the server and try again with a new connection, while the server should mitigate duplicated requests (reject or return a successful code).

Well, maybe that's the point of the article, because many web pages gets confused if you send duplicated requests to them.