Well step one is definitely discussing it with the mods/community. If they ignore you, or fail to provide a valid reason for the ruling, or abuse their powers and lock the thread, then you can escalate it to site staff through the Support Hub: https://www.speedrun.com/knowledgebase/supporthub

request the mod be removed LOL. Only if they are being really hostile to players though. Also, banning keyboards is elitist af and dumb for most games, but that's just my opinion. I played games without a keyboard for ages and still prefer it for SNES, genesis and NES [anything without a directional stick].