Chat Shown: commands only broken - displays all chats but prevents me from submitting commands with "cannot send chat message"

When I switch to Chat: commands only the chat window still shows ALL chat content but disables my ability to send send commands (like /plotme home), when I try it says "cannot send chat message"

I need this option because the chat content on the multiplayer server is often too rude to be displayed in public.

This seems the exact opposite of what should happen - show only command chats in the window and let me still chat. If I didn't want to use chats or commands at all I'd select "hide".

Setting chosen from:
ESC->Options->Chat Settings (Multiplayer Settings)-> Chat: commands only