you can leave the room, in amethyst.. ya just leave it. i don't think you can suppress the spam in pub chats in amethyst yet.. unless it's that people icon by the relay that i duno what does..
Discussion
I have left the room, it still shows up in my feed.
ouch, i feel like this may have happened to me at some point, you could always try clearing the cache, and/or app data, and then leave the room again right away.. CTRL-ALT-DELETE
This is how involved that problem:
1. Leave those rooms
2. Toggle off friends icon and global feed icon for all relay nodes except the paid nodes.

What is the "friends" icon BTW? I've been assuming it's for replies to messages.
Public chats
* Public chats :)
Thanks. I wonder if it might be useful be indicate in the relays view on Amethyst which ones are paid and which free. I think by default the paid ones are the ones with global turned on but might be helpful to have a reminder using some type of icon (like if someone changes their settings they might lose the info on which are paid).