Markdown has no comment syntax. What you're using is borrowed — and the one you picked decides who can read your note.
Neither the original Markdown document nor CommonMark defines a comment. Every trick is borrowed from HTML or from an unused link reference.
CommonMark passes it through as-is. Your browser skips it, so the page looks clean — but View Source and curl still show every word.
An unused link reference definition is consumed while parsing and never written out. Nothing about it reaches the HTML at all.
No blank line before the label. Four spaces of indentation. Inside a code fence. Or a renderer with raw HTML off — then it prints on the page.
Bio fields, comment boxes and CMS editors disable raw HTML to stop XSS. Paste a comment there and readers see the angle brackets.
Platforms that render your Markdown strip comment nodes before serving. The raw file in the public repo still carries the note in full.
Front matter is the one place with a real comment: a hash line never reaches the renderer. Anything sensitive doesn't belong in the file.
Every method rendered and pasted in unedited, plus the one that leaves nothing behind.