If you only read the Bohemia Interactive Community Wiki, no more information is collected than is typically collected in server logs by web sites in general.
If you contribute to the BI Community 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 (but see private logging below).
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.
To publish a page in the wiki, you are required to be logged in and you are identified by your user name. This may be your real name if you so choose, or you may choose to publish under a pseudonym, whatever user name you selected when you created your account.
Remember to log out or disconnect yourself after each session using a pseudonym on a shared computer, to avoid allowing others to use your identity.
The wiki will set a temporary session cookie (PHPSESSID) whenever you visit the site. If you do not intend to ever log in, you may deny this cookie, but you cannot log in without it. It will be deleted when you close your browser session.
More cookies may be set when you log in, to avoid typing in your user name (or optionally password) on your next visit. These last up to 30 days. You may clear these cookies after use if you are using a public machine and don't wish to expose your username to future users of the machine. (If so, clear the browser cache as well.)
Many aspects of the BI Community Wiki interactions depend on the reputation and respect that is built up through a history of valued contributions. User passwords are the only guarantee of the integrity of a user's edit history. All users are encouraged to select strong passwords and to never share them. No one shall knowingly expose the password of another user to public release either directly or indirectly.
Every time you visit a web page, you send a lot of information to the web server. Most web servers routinely maintain access logs with a portion of this information, which can be used to get an overall picture of what pages are popular, what other sites link to this one, and what web browsers people are using. It is not the intention of the BI Community Wiki to use this information to keep track of legitimate users.
These logs are used to produce the site statistics pages; the raw log data is not made public, and is normally discarded after a few weeks.
Sharing information with third parties
Except where otherwise specified, all text added to BI Community Wiki is available for reuse under the terms of the license specified in the license to Bohemia Interactive and other users.
Bohemia Interactive will not sell or share private information, such as email addresses, with third parties, unless you agree to release this information, or it is required by law to release the information.
Security of information
The Wikimedia Foundation makes no guarantee against unauthorized access to any information you provide. This information may be available to anyone with access to the servers. A partial list of those people can be found in the developers list.
Data on users, such as the times at which they edited and the number of edits they have made are publicly available via "user contributions" lists, and in aggregated forms published by other users. 
Deletion of content
Removing text from BI Community Wiki does not permanently delete it. In normal articles, anyone can look at a previous version and see what was there. If an article is "deleted", any user with "administrator" access on the wiki can see what was deleted.