That would be due to you not having the permissions rights to use that. AT the moment we do not have a plugin doing anything with /help so it would not give you any info that would be usefull anyways.
Sadly that is not a plugin. That is the way it looks on a vanilla server, Mojang changed the hook used for log in in and out so the plugin that we used to block them no longer works, Once it is updated we will implement it again and there will no longer be any log in/out messages.
Chat is very messed up. At the moment, i cannot do anything in chat, wether chatting, using kits, warps, tps, etc. I have tried re-logging and restarting the program to no avail. and I do not believe this is just a lag issue just a lag issue.