Right now the grid used to display log messages can be narrower or wider than the size of the window that contains it. If it's wider, you'll get a horizontal scroll bar. If it's narrower, there will be unused space on the right side of the window. This means that whenever you adjust the size of the window, or open a log for the first time, you usually end up resizing the last column in the grid so that it occupies the whole window.
It'd be nice if the grid would set itself to be at least as wide as the window it's in.