I am no staff, but I have been playing this server and survival servers in general for a long time so that I will make so suggestions to at least try to help these issues.
Compared to some larger servers I have played on, the chat is pretty clean and easy to follow (Some servers I have seen have 5 tags by each player name with a pointless "ding" sound whenever someone puts something into chat). On one of the older servers I used to play on, it was about the size of this server more or less, with all worlds, Hub, Survival, Creative, Hunger Games, and Shops where on the same chat with little tags by them that would say what world they are in, which I think this server implemented well with the abbreviations [sv], [ct], and [eqt], not in the way and cluttering the chat making it hard to read. I think there should be some simple alterations to the "/ch" command, where if you type "/ch survival' It won't say "You are now chatting in survival", it will instead say "You will now only see chat from survival." If you want to get real crazy, you could set a time so that players won't forget to re-active global and miss chat from other worlds, like "/ch survival 15". You could also make it so that if a player from another world says a player's name, the message with their name will appear in their chat, so that it will be possible for players to respond from a muted chat.
I personally like to see chat from all servers, because my friends switch between at different times. What I really find annoying is I don't know who is on ALL of the servers at one time by /list. I think /list should show players logged in across all servers, not just the one you are on. If not done with the command by itself, it could be done with extra parameters like "/list creative"
I think there should be a sub-nick on an RPGnick, so that you can put a cannon or well-known characters, fictional or otherwise, name over your own without erasing your old one, but in a different color so that people know something is different about it, but keep them blacklisted as a normal nick so that players don't get confused. If a play tries to do "/nick Fluttershy" it would return "We don't allow canon names as normal nicknames. If you are trying to roleplay as a character, do /rpgnick [nickname] then /ch RPG"
I know I just created a huge wall of text, and saying this is adding to it, but I hope this these suggestions help feed to the ideas for improvements to the server.