Labels

/w, /msg, /tell all say: Usage: /tell <player> <privateMessage>

/tell, /tellraw, /tp and /testfor don't work when using coordinate arguments.

/tellraw and /say have no success output and don't update command blocks

JSON requires quotes around the keys in the "/title" and "/tellraw" commands and NBT tags "pages", "Text1" .. "Text4"

Command /me does not resolve selectors if used by operator

Commands aliases do not display syntax help/tab complete correctly

You can message yourself using /tell