<includeonly /> is not valid wikitext markup, which is distracting.
Let's use <includeonly>…</includeonly> instead.
Bug: T250937
Change-Id: I9eac8b265eca16118d390da2628e0da7ca409ed8
The difference is that metaitems are not visible on the editing
surface, and their exact position is not preserved when the paragraph
containing them is edited.
This behavior is desirable for e.g. categories, but not for
<noinclude> and related tags, which are intentionally placed in
specific places in the text.
Note that we don't really have any editing interface for these nodes
yet. But you can see them (and they come with descriptions and links
to documentation pages), and delete or copy-paste them.
Bug: T250937
Change-Id: I104e7abbd650567df0e59813653c46a66d955d58
