The message viewer is obviously quite important for an MUA. There are some bugs reported for the message viewer component of kmail2, but there's no such component in bugzilla. Please add it with the following description: Bugs related to the message viewer of KMail, both standalone and integrated
Has this been discussed with the PIM developers?
The KMail maintainer is not interested in this new component. (not to mention it already exists for the kdepim product)
You should tell him about that component, because he doesn't seem to be aware of it. Thank you for the pointer and sorry for the noise.