alt Hacker NewsThe HN article title suggests a contradiction where there isn't one. The instruction set is just the spec -- the high-level contract that the silicon must implement, with many important details like cycle counts per instruction left unspecified. It implies very little about how you would actually implement the inner workings, which could be done in an almost infinite number of different ways (including simulating them on some completely different architecture). Compare "How do you sell a calculator design when the rules of arithmetic are free?"
RISC-V is pretty unoptimisable though; the industry has had its fair share of pretty lackluster MIPS and MIPS-like clones in embedded, and they've been mainly high-volume low-cost "cheap and good enough" SoCs. To be competitive with ARM and x86 you really need higher code density and better, more complex instructions.