Which HTML element makes the most sense for code annotation?

I'm working on a web app that has code listings. Certain lines of code have notes attached to them (think comments, but not inline code comments - more like an author explaining something).

When a user hovers over the footnote type indicator, a tooltip will display the comment.

Example code on jsFiddle

Now the questions

1. What element would make the most sense to wrap the comment indicator in? I toyed with the idea of <mark>, but I get the feeling that's a stretch. Somebody suggested the <object> tag could actually make sense. Again, not sure.
2. Is there an element that the actual footnot开发者_JS百科es (we're calling them annotations) should be wrapped in?

Any insight would be greatly appreciated.

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I was thinking that <aside> might be useful, but probably a footnote pattern is really the closest match.

Wikipedia uses <sup id="cite_ref-N"><a href="#cite_note-N">N</a></cite> for the indicator and <li id="cite_note-N">Note</li> for the note. You could do worse than follow that.