I was hoping for some article or wikipedia entry that would tie your comment with the parent's comment, and with the original article. Monomorphization is, to my understanding, taking a polymorphic function and instantiating it to the specific type requested. This is done at compile time. Now, the tool in this article interleaves debugging code with original source code. So the connection is... both monomorphization of generics/templates and this tool operate by emitting source code prior to compilation?
The original comment was about how both debugging and generics are being implemented with code generation before runtime in Go and described this as "unusual." The response was that this precise technique is how generics are implemented in many languages already; in fact, CFront (the original C++ compiler) was entirely implemented as code generation on top of C. The response specifically discussed generics, not debugging, so I'm not sure why you thought it was talking about debugging.