The search capability of Confluence is starting to fall behind that offered by many commercial knowledge products. In particular there is no ability in Confluence to specify synonym rings (a ring is a set of terms which have equivalent meaning - a term meaning a word or a phrase). This is useful for many reasons in particular knowledge domains (for example a user could enter either an acronym or its equivalent long form or other predefined synonym into the search box and the indexed Content Entity Objects would return documents that contain any of them). Also there is no ability to predetermine that certain Content Entity Objects are always matched to particular search terms in order to guarantee that desired content is returned if someone uses a particular search term. There are no extensions employed by Confluence to allow search to provide faceted search capabilities (for example, see http://drupal.org/project/faceted_search or SOLR )
These features are important to enhancing the functionality of knowledgebases and providing users with more fine tuned search capability that, if used skillfully, are more likely to produce useful and quick access to content for the average non-technical user without having to be a search query guru.
These features should be implemented in search in such a way that they can be configured per space or globally and that plugins such as metadata and advanced search can take advantage of the added features, being able to extend or modify their behavior for particular purposes.
Finally, there should be the option to index rendered wiki pages such that wiki markup is never shown to the user in search results.
Make custom metadata (ala metadata plugin) capability and metadata reporting/searching an integrated part of the base Confluence product
Incorporate these features into the Remote SOAP interface.
The features should be configurable primarily by either site and/or space administrators depending on scope.
Some of these features have various open source implementations that are demonstrated or have become commercial products. Products such as Sharepoint 2007 and others have implemented some of these features or are rumored to be adding them in the near future.
Note: I was reminded that this is probably too broad for a feature request. I apologize for that. I just wanted to tie a lot of related aspects of the search improvements I was requesting together (as a wish list).