When I run this script, it makes it so you can't use the "/" key to open chat anymore. and I have no idea why. If nobody can answer I will report it as an engine bug on the devforums.
game:GetService("StarterGui"):SetCore("CoreGuiChatConnections", {ChatWindow = {}})
Anything in that core, even with a correct chatwindow table, still breaks the / key to open chat.
Use this:
game:GetService("StarterGui"):SetCore("CoreGuiChatConnections",false)
This make the player unable to break the chat by pressing '/' key, and avoid people chat in chat too. Hope I helped. Bye!