ikiwiki-syntax extends vim-markdown to add support for [[!directive ...]] and [[internal link]].
This probably worked four years ago when that plugin was last updated, but now it doesn't work unless those links or directives are inside lists - outside of them, mkdNonListItem from vim-markdown seems to take priority somehow, and the directives/internal links don't match at all.
This probably isn't an issue with vim-markdown, but this project is actually active and ikiwiki-syntax isn't, so I figured i might have better luck asking here.
However, commenting out the line that says syn region mkdNonListItemBlock ... in vim-markdown "fixes" it for me, so maybe it's really something that could be fixed on this side. I know nothing about vim syntax files, so I have no idea why that line is needed :D
Any pointers will be appreciated.