its a delimiter not a sigil
Well, it's a section sign, but lawyers sometimes call it Sigil. (I know that namespace is already occupied in this circle.)
Because its not on the standard keyboard!
If you're on a Mac it's quite easy to make, and if you're on Ubuntu it's pretty easy to make. On Windows too, I still remember
Alt + Num0141from typing Spanish on a US keyboard.
Anyway, I admit this approach is not for everybody. I like your suggestions (but I don't have a key for «).