When you install the extension it warns you that it needs access to "Your browsing history". I can understand why it needs your HN data, but why your browsing history? (or is that message simply misleading)
Any chrome extension which uses a 'background page' is listed as accessing your browsing history. This is because a background page (think of it as a daemon) knows which tabs you open and where you navigate and could theoretically store or transmit that data.
This is weird to me too, because I dont request permission for the history. I will look it up.