Issue: Convert HEADING to XenForo HEADLINE

While this is technically feasible as a BB-Code conversion, I would strongly advise against it. VaultWiki's H tag provides functionality that XenForo's HEADING tag does not. For many functions, I suppose they could be acceptable losses (like the number of possible levels, article splitting, collapsing/precollapsing, sharing options, etc).

However, section synonyms, or at least the most intuitive way to manage them (via the heading they point to), would be lost.

In the worst example, once you perform such a conversion, you would be completely unable to edit individual sections in wiki content anymore, because XenForo's tag does not support that. If this conversion was performed now, the wiki would be unable to benefit from a future upgrade script that moves the section functionality to an entity rather than a BB-Code, because there would be no existing sections anymore. So I think the safest course of action, if we adopt a converter, would be to provide it only after whatever future version moves section functionality.