Inside the clientbound chat message packet, there is a "sender" field to identify the chat message's author with their's player UUID.
Upon sending a chat message as a player (or receiving one from another player), the client will freeze for about a second, likely for the reasons leedagee mentioned above. The client no longer experiences this issue for future chat messages that are sent/received, until it has been restarted (from my experience).
The issue however cannot be reproduced if the sender field is empty, e.g. system messages using tellraw or modified server software where the server simply doesn't send the sender field / sets it to a blank UUID on player messages. Oddly enough, this issue also cannot be reproduced on systems with AMD graphics. I've only been able to reproduce it on systems with NVIDIA graphics.
Ah yes, that does seem like a valid duplicate issue. I'll go report my findings over there, seems like someone else in the comments has reported some good information too. Thanks.
clx_
Sharing my findings from MC-235836
Inside the clientbound chat message packet, there is a "sender" field to identify the chat message's author with their's player UUID.
Upon sending a chat message as a player (or receiving one from another player), the client will freeze for about a second, likely for the reasons leedagee mentioned above. The client no longer experiences this issue for future chat messages that are sent/received, until it has been restarted (from my experience).
The issue however cannot be reproduced if the sender field is empty, e.g. system messages using tellraw or modified server software where the server simply doesn't send the sender field / sets it to a blank UUID on player messages. Oddly enough, this issue also cannot be reproduced on systems with AMD graphics. I've only been able to reproduce it on systems with NVIDIA graphics.