alt Hacker NewsWASM is a sandbox. It doesn't obviate memory safety measures elsewhere. A program with a buffer overflow running in WASM can still be exploited to do anything that program can do within in WASM sandbox, e.g. disclose information it shouldn't. WASM ensures such a program can't escape its container, but memory safety bugs within a container can still be plenty harmful.
At least WASM can be added incrementally. Fil-C is all or nothing and it cannot be used without rebuilding everything. In that respect a sandbox ranks lower in comprehensiveness but higher in practicality and that's the main issue with Fil-C. It's extremely impressive but it's not a practical solution for C's memory safety issues.