I used to be a regular on /m/ for about a year and a half so I know what's discussed there. However I was under the impression that it was for supposed to be there for mecha discussions.
if the rules state otherwise i'd like to see it. All I saw on the rules page was:
/m/ - Mecha
1. All mecha and mecha-related (ex: core fighter, mecha girl, model) images are allowed.