This is a bug that needs to be urgently fixed.
There have been multiple scenarios when I have been forced to kick out players due to spamming the chat. Unfortunately, while they weren't able to race anymore, they could still send messages. It appears that I, as a host, cannot see these messages, but the other players still can, which defeats the purpose of kicking these players out in the first place.
There are players who are genuinely bothered or easily distracted by this kind of message spam, which is why I believe this issue needs to be resolved next update, if possible.
Report issues and bugs here.