SUMMARY Messages get rapidly hidden in long threads (thread view). This is not a rare case in collaborative projects and mailing lists. Navigation then becomes blind. STEPS TO REPRODUCE 1. Go to a thread of 10-100 emails 2. Navigate down the thread in the message list OBSERVED RESULT Emails rapidly become invisible because of the right shift from one email to another down in the thread EXPECTED RESULT All emails should be visible in the thread of message list. ADDITIONAL INFORMATION There are probably cool solutions to this like the one implemented by mailspring and other email clients, but I think a solution easy to implement given the current architecture would be to right shift only once, from the head message of the thread to the rest. This would allow differentiating between messages belonging to a thread from others, while strongly diminishing the blinding effect. One can say that it misses information about subthreads, but correct display of subthreads is tricky and I for one don't care much about them (frankly I think that not being able to see messages is more important than how subthreads are organized). Also, this (plain thread view) could be an additional option to display the message list (in addition to the current subthread structure).
I agree this is a painful papercut from Kmail currently. An alternative, easy (?) to implement fix, would to revert the sorting of messages in the threads (akin to a "Conversation view" were new messages are at the top). At least this way, new messages are readable and only old messages in the threads aren't (but they aren't as valuable normally...).