At least Nvim allows me to turn that shit off, select a plugin that matches my preferences, or program a keyboard shortcut to toggle rendering on and off. The MS Editor just unilaterally decides that your file should now end in .md, because it contains what MS considers markdown formatting, as if there's no way a plain text file could contain lines beginning with # (although, granted, you have to press one of the formatting buttons first, before the editor switches to "markdown mode" and starts behaving that way).