Tucker S
Comments
To answer your fist question, the bug was there even before joining the server. Almost all conditions have been changed without any difference on the devices that show this.
It also does not help to reload the game and use a different world type.
Update: I just tested this on yet another device, and iPhone 6S, without this problem. I would normally dismiss this as an issue with just my device, but it has been present on two or three devices on different worlds but other devices.
I have seen these problems on my and others mobile devices in single player, multiplayer, and on the client side of a personal server. I also observed this in the same version of Minecraft Windows 10 Edition running the same version. On the host side of the server, running /help works like normal.
The screenshots were taken on a NukkitX server, as this was most convenient for me, but it is present in other devices. By now it has been a while ago, so perhaps Mojang quickly patched this.