That was fantastic and sad. And beautiful in a way. I wonder if Bliss ever tried to convey his ideas to Shirley McNaughton using the Bliss symbols.

I've done some work grading state standardized tests for children with disabilities and never seen Bliss symbols, though I'm American and as that episode of Radiolab mentions, Bliss symbols are mostly used in Canada and Sweden these days. Instead, children who have difficulty communicating use either American Sign Language captured on video or indicate their responses using Mayer-Johnson symbols like these:

I think in some sense, Bliss was right to be angry. Sign languages tend not to be mutually intelligible, so not only are native ASL (which is not an analog of English, but a distinct language with its own grammar and vocabulary) speakers isolated from other Americans, but from other native sign language speakers from other countries or other sign languages within the country like the Martha's Vineyard Sign Language which went extinct in 1952.

A universal language would be hard to maintain though, as languages adapt to what the speakers do in their everyday lives. For example, in many Asian languages, there are words for the many different types of rice and even words related to rice planting, production and culinary preparation while in English, those words do not exist, though they can be described.

The fact that Bliss' interest was not in a spoken language, but rather a written language is fascinating, though even languages that are only written and not spoken as everyday means of communication, have their quirks too (as in the grammar and construction of phrases, etc.)