We are expanding support of lightweight formatting to include additional Markdown syntax features. This includes strikethrough formatting and nested lists. To get started, explore these new options in the formatting toolbar, keyboard shortcuts, or by editing the Markdown syntax directly.
Source: Microsoft.
It’s a text editor how could it not support markdown?
most simple text editors do not support markdown.
The whole point of markdown is that it’s readable as plaintext.
It would have made more sense to make Edge render markdown.