I highly object to this kind of nudging (or at least to it being a default - as I see some applications for it in business use).
In non-business usecases such technical means of telling your communication partner that he/she has seen or read something is a presumptuous intrusion into my right to decide for myself when and how I reply to a message.
I decide when I answer! It is my time and my decision to reply even far later than when I read the message, yet those kind of nudging mechanisms try build social pressure to force me to answer ASAP. I detest such things to the max!
That being said: please! If you do introduce sth. like that, don’t make it the default!