Wikitext appearing in transclusion dialog
The underlying cause of this might be covered in bug 48231 or bug 51217 or others ... I thought I saw a bug about this, but cant find it now.
[[template:multicol]] with wikisyntax inside it results in the attached screenshot, with wikitext visible in the transclusion dialog as 'Content' blocks.
Section headers & list items also cause this; see the last block here:
If it helps, this issue is present on one of the parsoid topfails:
BeginKolommen occurs on nlwp 3047 times. 11362 times in enwp. 8861 times in eswp. 40985 times on itwp!, which is roughly 4% of the content pages.
Confirmed this is happening on every itwp invocation that I edit