The B double vertical strokes is a Unicode symbol? What is its code? I can't find it on any list of Unicode symbols (maybe I'm not looking in the right place?).
Yep. Unicode defines symbols like this using "combining" characters
(the "already combined" characters exist only for compatibility with legacy encodings such as Latin-1), so for B⃦ you do:
This works to some extent for all possible combinations (apparently some people are getting blocks, though?).
From there, fonts can specialize with "ligatures" (renderings that represent a sequence of characters) - which is where things can definitely use improvement.
I see...so it will require two codes to generate...in time I suppose the implementation will catch up with the spec. I get Bbox on my iPad on iOS 6.