What I miss is some way to copy the rich text with formatting, but without any theming. This allow me to keep a markdown version which I work with, but to easily share a rich text version, via e.g. email, with non-markdown users.
Currently I can either copy and paste with all formatting, which seems to include a background color, or paste without any formatting, which removes the headers.
Copying also seems to skip any mathematics that is in the document. My current workaround is to open the document in Typora, which has a “Copy without theme styling” option. It also seems like they include mathematics as an image in the copied text.