Check this Wikipedia article for example, and open the VisualEditor.

All the list-defined references are displayed as "This reference is defined in a template or other generated block, and for now can only be previewed in source mode", and editing them has to be done with the source code editor.

This happens when the references are in the template {{reflist|refs=. List-defined references that are in <references> are properly displayed, although editing them is not flawless, as noted in this bug report.

See this discussion on Wikipedia, and this one on the MediaWiki. Feel free to comment on these discussions if you have important new information to share.