Wikimedia Bugzilla is closed!

One common user error is to save a page containing a <ref> tag but no corresponding </ref> tag (or in some cases, the user meant <ref/> instead); the tag is used in connection with the Cite extension. Whenever either of the following cases is true:
- An HTML-like starting tag is used to invoke an extension, but there is no matching end tag
- Between the starting and ending tags used to invoke an extension is a duplicate of the starting tag (which almost inevitably means that an ending tag has been missed earlier)
it would make sense to warn the user that they've almost certainly made a mistake; the current situation is that part of the page ends up being blanked, confusing the user who has no obvious means of fixing it unless they are skilled in markup. I suggest that in such cases, the 'Save page' option should instead do a preview, placing up a warning that there are probably problems with the markup and suggesting what went wrong; as a safeguard, a second save in a row should work as normal. (This method is already used for the optional warning when no edit summary is given.)