To avoid things like http://en.wikipedia.org/w/index.php?oldid=230829925&action=edit it would be great if it were possible to have customizable messages appear above the edit form for certain namespaces or articles.
Using a standardized format like MediaWiki:Notice-edit-<page_title> or something similar, notices about article restrictions or particular concerns with a given page (or namespace) could be displayed regardless of whether someone uses the edit tab or section edits. The Template: namespace could have a message that explains the purpose and function of templates and their syntax, etc.
Apologies if this is already filed elsewhere. I couldn't find anything similar.