If you only read the wiki pages, no more information is collected than is typically collected in server logs by web sites in general.
If you contribute to the wiki, you are publishing every word you post publicly. If you write something, assume that it will be retained forever. This includes articles, user pages and talk pages. Some limited exceptions are described below.
Publishing on the wiki and public data
Simply visiting the web site does not expose your identity publicly.
When you edit any page in the wiki, you are publishing a document. This is a public act, and you are identified publicly with that edit as its author.