I couldn't find the right component as this is in the website instead of an actual part of Gentoo but I found this accidentally and I wanted to report it before anyone takes advantage of it. If you type any "-" into the wiki.gentoo.org search box a database error gets returned. If there is sanitization going on I think a better error page would be the simplest course of action but I didn't want to break anything by finding out if that was the case. Ideally users should be able to search for something with a "-" in it so I think it should be fixed either way.
My observations: - Searching for strings containing a - works as intended. - /^-+/ is a 'problem'. - The resulting queries are properly escaped, the '-' is simply not expected there in the mysql fulltext query. This might be fixed in a recent mediawiki version and an update of our site might fix it. Otherwise, I don't see a need for more investigation and/or fixing. Thanks for your report and concern.
