How to reproduce:
When replying to a mail, the own text is written underneath the quote

Actual Outcome:
When replying to mails with a lot of text, you have to scroll down and the important fields disappear from view → you have to scroll up again to view and edit them

Expected Outcome:
Upper part of the window (including fields like "from", "to", "subject" should be permanently fixed to their position
Even better: Own text appears above the quote

This can be realized by clicking "settings" → "composing messages" → "when replying" → "start new message above the quote"

Solution:
Change default setting to "start new messages above the quote"