As a small, iterative step towards T321217: Get rid of Cite formatting i18n messages that are not actually localized we suggest to empty (but not delete) the two messages cite_error and cite_warning.

• cite_error currently says "Cite error: $1" and should be changed to "$1" or "-".
• cite_warning currently says "Cite warning: $1" and should be changed the same way.

Reasoning:

• The problems with these two messages have been discussed in T30843: Cite error uses lego messages breaking localisation and customisation, should be deprecated. The common prefix doesn't help much, but makes localizing the individual error messages harder. Most of the errors already talk about the context they apply to, some don't, resulting in inconsistent experience. Instead, every messages should be self-contained and explain what it is about.
• Just deleting the messages is not an option as long as the communities use them heavily for all kinds of customizations (tracking categories, custom templates).
• …?

To do:

• Update the individual error messages so they are easy to understand without the prefix.
• Change the two prefix messages to contain nothing but "$1", possibly even "-" to mark them as disabled.
• Update the code to act appropriately when the messages are disabled → https://gerrit.wikimedia.org/r/995055
• Check the existing overrides on the Wikimedia wikis and see if some need to be updated. Some can probably be deleted. (Compare the related T335129.)
• What would need to be done to remove the two messages entirely?
• …?