If your server doesn't use Skript's "send formatted" effect, you're in the clear.
Basically if your server uses "send formatted", users can sudo other users when they click the chat message.
Assuming the "send formatted" is in your [item] code, here's a solution:
on chat:
if message contains "[item]":
cancel event
replace all "<" and ">" with "" in message
# do [item] stuff
send formatted "&7%player%&8: &f%message%" to all players
else:
set chat format to "&7%player%&8: &f%message%"
It's extremely easy to abuse "send formatted" so for server security I'm not explaining how to use it.