On a chat message, the client will check if that player is blocked or not.
This is an API lookup. But this does not happen on a thread.
This will cause a lag on every (or some) chat message.
This mod aims to fix that, by doing the chat message handling on other threads.
Almost noone is using the chat restriction, for them, it is faster to avoid the whole API lookup:
mod doing that by @adryd325
adryd325/chat-lag-fix/
And the proper caching of the blocked user list is part of Blanket!:
Blanket/.../YggdrasilUserApiService_syncBlockListMixin.java
CurseForge/Blanket
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