I've read Are plan9 questions on-topic?, and it seems like there wasn't really a consensus. The discussion was started, but never really finished. Plus, that was a couple years ago, there are new people, etc.
So, are Plan 9 questions on-topic? Plan 9 from Bell Labs book seems to indicate that they are, since it haven't been closed.
Other questions found by looking at plan9:
- What aspects of Plan 9 have made their way into Unix? - this is a UNIX-focused question, not a Plan 9-focused question. Therefore, irrelevant to this discussion
- How to run programs with arguments like 'arg=val' (e.g. dd) in rc shell (Linux version ported from Plan9 OS)? - this is about the port of
rcto UNIX done as a part of plan9port. It is about
rcon Linux, not Plan 9 in general. Therefore, irrelevant(ish) to this discussion
- https://unix.stackexchange.com/q/8297/29146 - closed due to the fact that it was too broad, not due to the fact that it was about Plan 9. Therefore, not an indication of consensus, and therefore, irrelevant
If anyone thinks this question is unwarranted and Are plan9 questions on-topic? still represents community consensus, feel free to vote to close as a dupe.