• there seems to be a consensus memory should be imported for wasi-threads. clarification: Clarify how shared memories are created and shared #20
• on the other hand, it's said that memory should be exported in wasi: https://github.com/WebAssembly/WASI/blob/main/legacy/application-abi.md#current-unstable-abi
• it's a bit redundant to both import and export a memory.
• a side note: released versions of LLVM wasm-ld doesn't seem to support both import and export memory. https://reviews.llvm.org/D135898

discussions:
WebAssembly/wasi-libc#369 (comment)
#19 (comment)
WebAssembly/WASI#48 (comment)