Categories in general are broken and they have been so for several years now. Pages that were added to categories before that show properly, new pages (mostly) do not. Images for some reason do get added to category pages, even though the regular pages do not. New hidden categories are not hidden (when a category is hidden, it should not be displayed in the categories list).

The wiki has also other issues. Here are some tips if you start editing.

Sooner than later, you are sure to stumble upon the "Forbidden 403" error. This can happen usually for two reasons: the text you are submitting contains certain banned keywords (you are not getting told which ones) or the submitted text is too long (editing a long page is not an excuse). There are workarounds. You can edit only a section instead of the entire page. You can avoid the blacklisted "styIe=" phrase by replacing it with "style{{=}}". By the way, you can also get this error here on the forums and on the support ticket page.

Also, when you reupload an image, it may look as if you uploaded the old image again. Do not reuplad the image, the image is there, it just needs a day or so to update. (I am not actually sure if this is still an issue, but it used to be in the past.)