Many members of my community have complained about the following scenario: Go to a forum you want to search. Enter a search query top right. Hit enter / "Search". You are not completely happy with the results and enter something different in the search box top right. Suddenly the search is site-wide. People expected the search to still work in the scope of the forum you wanted to search originally and not suddenly across the entire site. I have been telling them to use the tiny button called "Search Again" to modify their query, but I think this is a usability issue as many people have reported it as a bug and thought it was bad.