The other day, I encountered some issues using the “Markdown Preview” package with .md files, so I’m making a note.
This might not be limited to Markdown, but when you preview, the original text can sometimes be rewritten.
It’s especially dangerous when writing “code” like HTML directly. It gets automatically escaped. (Perhaps wrapping it in <code> would work.
When embedding an iframe, the iframe is reflected in the view, which creates chaos.
As a countermeasure, when viewing .MD files, you should either take a backup or be careful with the character count, viewing in small increments.