As I wrote before, things will improve, HTML mails will be viewed correctly in the next version. I suggest to take a look at the respective Delta Chat repositories on Github, where you can see each and every action in detail, even if you are no developer. (Neither am I.)
Projects like this one are not that straight forward. Perspectives must be found in every single detail: Which database/UX do I rely on when I want my app to run on different operating systems? How do I cope with APIs, different display views, etc.? This is an extremely huge project, and everyone is very committed. Compatibility to MUAs (classic mail clients, almost finished) and a change towards a different database layer are currently on the todo list. And fixing issues 24/7, of course.
So, please be patient and wait for the next release. And there is always room for improvement, we all know thatâŚ