Ow...
That's new... the "8" is no more eligible to be a rotator?... Since when?
The fact that the "8" is made with a small ball and a large ball is irrelevant for me. It's only a stylistic difference, which depends of the font you use to write the digit. Some have a perfectly symmetric "8" (as in the 1937 and 1954 series), others have slightly assymetric "8" in the most recent series (Multicolor, Birds and Journey's). But even slightly assymetric, an upside down "8" still looks as an "8". And there is no risk to confuse this digit with an existent letter.
It's not the case with the "1", which can be confused with an "I" when both are written in a too plain style. That's why the "I" is rarely used in the codes using letters (license plates, postal codes, etc.), and even in this case, you use a font showing the "I" with disproportionnaly large serifs to make it quite different looking from an "1". Just look at the notes which have an "I" in the serial...(ANI, EYI, EZI), to see the difference. The "1" is almost always written with a small "notch" at left, but not always with a serif at the bottom. So when an "1" is read upside down, it's evident that the digit is upside down.
The general idea for the rotator is when the number is read upside down, it's in principle impossible to tell that the number is upside down, since we read the very same number.
