A text file only contains data that represents characters on the screen, while “binary file” is used to refer to any other file that isn’t meant to be viewed or edited as text.
If you open a (small) image file with notepad you will see a lot of gibberish. This is what happens when you try to view a binary (in other words, non-text) file as text.
But vendors are already providing a (somewhat) standard way of displaying that content through regular notifications. If I were to build a unified inbox like this, it would look more or less like a persistent view of the notifications panel from Android.
I have not tried this with Obsidian yet, but I know that Markdeep allows you to render .md files on the fly as HTML by appending some javascript to the unmodified markdown.