Yes, IMHO as well, emailing and chatting are very different. And deltachat is only working on building the chat side of things.
Yet Email-chat flourishes based on good cooperation with email.
There are really very much of intricate things involved in finding and improving a universal usability.
Just recently another user found a really nice way to solve a lot of group chat manageability and email interoperation problems with an absolutely non-obtrusive integration of a “chat topic” filter. I didn’t add the “subject handling” compatibility to the basic usability wiki page before, because the ideas just didn’t feel like native chat solutions yet. But now, allowing for these optional “chat topics”, some day, seems like the sought after, “native” but compatible solution.
Concerning the most basic usability, let me just point out one cooperative solution for a very basic problem, the double notifications that happen in the chat client and the email client. Over time only one way was found, that is considerably simple and can work reliably in all cases universally (not withstanding other more specific, and complicated solutions).
The simple solution is, to disable the (audio & visual) notifications in the email client, and letting deltachat also generate notifications about new emails in the INBOX (that will open the email app). The chat client is the only one that can (and already does) the distinguishing between chat messages (text and administrative) and emails.
Adding optional notifications for emails to deltachat is maybe a 5% effort on top of what was needed anyway, and what is already implemented. So, it’s rather a really cheap solution actually, considering it is providing a solution to a really general usability problem, and it is simple enough to configure (or maybe even auto configure) for less technical users.