Historically, TOC was never made to work outside of wiki content due to design issues in the post cache of regular posts (except in VaultWiki 3, where an option was chosen to use the wiki parser for certain regular posts). There are other ways to handle it, but none that are currently in core. There are a number of BB-Codes that do not work in non-wiki content for similar reasons:
- TOC
- FOOTNOTE
- REFLIST
- TEMPLATE (and template-related BB-Codes)
For TOC, FOOTNOTE, and REFLIST, it is relatively easy to add support, but required some outside-the-box thinking before we realized it for things like WIDGET and GALLERY.
For TEMPLATE, it requires a lot more work.