It is useful to comment out text in the source document, which will not be displayed in the final output document. For this purpose, we can use the HTML syntax <!-- your comment -->. The comments will not be displayed in any output format.

Comments can span either a single line or multiple lines. This may be useful for you to write draft content. If you use RStudio, you can use the keyboard shortcut Ctrl + Shift + C (Command + Shift + C on macOS) to comment out a line of text.