HTML comment conventions

Answer 1

You need at least <!-- --> to have a comment, and yes, you should avoid having "--" in the middle of the comment; the "--" are the actual comment delimiters. Other than that, you can just prefix it with any string and I think you'll be good -- e.g., <!--JEREMY_RUDD: -->.

However, storing data in comments sounds like a suboptimal idea. Can you elaborate on this? Have you considered whether, say, something like JSON might not be more appropriate?