I am starting this thread to serve as an ongoing repository for Category related discussions.

SirKitKat and I are doing some major back-end construction in the Wiki. If there are any questions on Categories please let us know. Our work is not changing any Category operations, but one thing in particular we will be monitoring is what links to the main category called Category:Index.
Guidelines for linking to the Category Index:

• Do not link a Category to the Index without first reviewing the proposal here.
• The Index should only connect to aggregated Categories.
• Categories from one country should be aggregated into a single country category, before it can be considered linking to the Index.
• The Index requires a common language. However, when an aggregated Category is in a non-English Language [[Category:Deutsch]], simply rename the category to include the English of that word followed by the local langauge [[Category:German-Deutsch]].
• We generally follow the Wikipedia Category standards except where noted due to differences.

The Wiki includes some special pages specific to Categories:

• All categories
• Uncategorized categories - These do not reference a parent category.
• Unused categories - no pages yet link to them.
• Wanted categories - these category pages simply do not have any Wiki markup on them to tell the user their purpose.

Read the Wikipedia Help article on Categories for more information.

(Note there was an earlier Category thread with a few Category questions and comments.)