Thanks for the tip and explanation.
In a way it also explains why the # sign is often used. The # is part of 'Low ASCII', a very basic character set, and therefore easily displayed, as easy as the letter A or B. There are good reasons to use the UFT-8 character set, and good reasons not to, and instead use some language specific character set. Some subtitlers choose not to use UTF-8 and so they cannot use ♪ or ♫. That's where the # comes in.