Created attachment 8 Regular MUC window for comparison
Additional scrolling bars sometimes appear in a MUC window with It'sAllTextcreated
Created attachment 7 MUC window with additional scrolling bars With Firefox and either the Vimperator or Pentadactyl plugin activated, additional scrolling bars appear (both vertical and horizontal). This occurs mainly when hovering the mouse over or clicking on the typing zone. When the typing zone is focused. I'm attaching two screenshots to show the regular window and the one with the bars.
OK so it appears this has nothing to do with Pentadactyl or Vimperator, but with the “It's All Text!” extension. Not sure you'll be able to fix this…