I'd request to have time and date shown on each email opened without the need to either click on sender nor the need of opening the header to read through ugly code. I think there is space to implement this without doubt, it's just too important to hide it.
Other requests on k9 page (page recommended to check here):
https://forum.k9mail.app/t/display-time-and-date-of-message/6196
Couldn't find similiar posting through search function.