Inputboxes can be added both via <inputbox>[params]</inputbox> or via {{#tag:inputbox|parameters}}.
<inputbox> type = comment hidden = yes buttonlabel = FooBar </inputbox>
and:
{{#tag:inputbox | type = comment | hidden = yes | buttonlabel = FooBar}}
should both render the same output, but when using the later, the hidden attribute as well as the buttonlabel one seems to be ignored.
You can see a comparison at https://www.mediawiki.org/w/index.php?title=Project:Sandbox&oldid=3646185