Currently, it is not possible to have an empty list item, for example, in:
* A
*
* B
or in:
# A
#
# B
The middle list item will be removed. We (the parsing team) would like
to change that, since it is counter-intuitive and makes things
difficult for VisualEditor.
The challenge is that we suspect some templates are taking advantage
of the removal of empty list items, as a shortcut to omit a list item
when a parameter is empty. Such templates will have to be migrated to
explicitly omit the affected list items. So we are planning on
introducing logging and tools which will allow this problem to be
quantified and fixed.
A change was recently merged which causes empty list items to be
hidden with CSS, instead of removing them altogether. This change will
be deployed next week as part of the usual weekly release train. This
should not cause any visible changes. However it does enable
client-side tools to be developed which will show an article with
empty list items included, the way we imagine it will ultimately be
rendered.
For more information, see:
https://gerrit.wikimedia.org/r/#/c/246148/
https://phabricator.wikimedia.org/T49673
-- Tim Starling