Go to settings and turn off "Show Number of Visits In Browser Icon" and see if that helps. If that helps, then perhaps I need to disable that setting by default on install.

Edit 1: "Removing the history for a link causes the browser's read/unread highlighting for that link to show as "unread"". I think that the browser uses the history to determine whether a link is unread or not, so if you delete the history, the link will show as unread.

Also this extension works best with e10s enabled which would probably solve your scrolling issue.