The bug happened when I used /essentialcommands rules, then I was kicked out of the server.

The error message:

And this is my rules.txt:

啊什么？你还想开挂？
------------服务器规则------------
1. 不要开挂
2. 注意你的言行
3. 不要人身攻击
-----------------------------------

It's in Chinese, I don't know if this is the reason for the error.

Hm. Definitely a bug. Time to learn how java does text encoding...

Added some text parsing enhancements here: 028561b

I was unable to reproduce your issue with that rules.txt, however, so I'm not 100% sure this will have any effect for your particular case.

lmk if the issue persists. I'm not sure what is happening atm, though. This appears to be happening in the network code somewhere, which is strange to me.