Thanks for suggestion to dig into HTML5 data stuff; I'll study the matter. Nevertheless: is HTML5 already in use? If it isn't, when it will be introduced into any wiki?
I dind't find in your answers a sound reason to strip away html comments but that they will be useless when using html5; I'm viewed as a "data maniac" into it.wikisource, we use any trick to manage data/metadata (cookies, microformats, labeled sections...) , and a good serialized JSON object, automatically built by js at upload of pages and wrapped into a html comment, would be very useful for our in the past with no overload of code/of servers.
Alex brollo