Being able to filter out chat from players on other servers might be a good option. However, I think that once the novelty wears off, it will settle down. Yes, the castle is going to be really busy from now on, but I don't think it will be unbearably so. Once the lag is taken care of and people get used to the newness of it all, I think it will be easier to pop in, quickly do what you need to, then leave again....like a lot of people currently do. This may also mean that the tavern might get more use as the server hangout spot, which could be neat!
The biggest issue may be that there are now gonna be 20 times as many low levels begging for free stuff...new players or spammers who either can't comprehend that you can't trade cross-server, or just like bugging people.
For everyone who is upset about the lag, please give VR a few days to make adjustments and do their best to fix the lag. It is unfortunate, but give them the chance to optimize and fix it. Also realize that the spam is really bad right now simply because everyone is going to the castle and purposefully spamming it, give it a few days and I'm sure it will calm down.
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