Wikimedia Foundation: Welcome to Wikipedia! Here’s what we’re doing to help you stick around

That’s explicit feedback. Wikipedia, however, has an implicit feedback system. It must infer from its data how a user feels about one of its articles, which is harder to do; if someone edits an article, do they like it? Or do they contribute in order to fix the issues they see in the article, even though they are not necessarily interested in the subject? You can’t tell.