C as an intermediate language (2012)

Yes and no. You can, but if you wrote your runtime in e.g. Haskell or Python you'd lose most of the advantages the article describes - debugging and tracing would be much more complicated for anything that called into the runtime, and profiling would become very difficult.

As a linkage format C is both too high-level (it provides a lot of facilities that are irrelevant to this use case - so while C may be ubiquitous now, I suspect it's much easier to implement an interpreter from scratch for something like LLVM bytecode) and too low-level (it exposes the host machine's memory model, making it inherently unportable). Use the right tool for the job - programming languages for writing programs in, intermediate representations for code for representing intermediate code.