Due to the changes in 1.13, clients will send a tab completion request
for all bukkit commands in order to factor in the lack of support for
brigadier and provide backwards support in the API.
Craftbukkit, however; has moved the chat spam limiter to also interact
with the tab completion request, which while good for avoiding abuse,
causes 1.13 clients to easilly be kicked from a server in bukkit due
to this. Removing the spam limit could cause issues for servers, however,
there is no way for servers to manipulate this without blindly cancelling
kick events, which only causes additional complications. This also causes
issues in that the tab spam limit and chat share the same field but different
limits, meaning that a player having typed a long command may be kicked from
the server.
Splitting the field up and making it configurable allows for server owners
to take the burden of this into their own hand without having to rely on
plugins doing unsafe things.
This patch has been applied to 1.12.2 in order to allow people using
plugins which allow clients of newer versions to connect, this is
not a common practice, however is being done as a level of nicety
given the current status of 1.13
Shane Freeder