When setting the prefer HTML instead of plain text, the messages are presented as HTML, but after restarting kmail the emails are presented as plain text.
The setting still exists but it is not respected. If you disable it and re-enable it, it then presents the messages as HTML again.
This happens every time I start kmail.

Reproducible: Always

Steps to Reproduce:
1. Select prefer HTML instead of plain text
2. See HTML messages
3. Restart kmail

Actual Results:  
Messages are not seen as HTML, regardless of the setting to prefer HTML.

Expected Results:  
Messages should be shown as HTML every time.