At least in my OS/X terminal using the "Monaco" font (which I think is the default), the final one (U+2588) doesn't descend as far as the rest of the characters. It really produces some ugly output with that one included.
Including the space character means that you lose a nice baseline if the input is fairly sparse, so it looks less like a bar graph and more like just some random blobs.
Including the space character means that you lose a nice baseline if the input is fairly sparse, so it looks less like a bar graph and more like just some random blobs.