Use the comment begin marker (<!--) and end marker (-->) as shown:
<!-- text here is completely ignored -->
The HelpTag software ignores all markup between the <!-- and -->. A comment cannot be nested within another comment.
Here's an example that has two comments, a line before the paragraph, and a single word within the paragraph.
<!-- Here is my rough draft of the introduction: --> Welcome to my application. This software is <!-- perhaps --> the fastest and most efficient software you'll ever own.