SUMMARY:
- Debug coordinates and other gameplay-relevanted info (like pointed) in the debug screen will be hidden for unprivileged players
- To get the full debug screen back, players will need the "basic_debug" privilege
- Game makers who want to expose coordinates should do so via a mod / HUD elements and not rely on the debug screen
There will be an important change in the next minor version of Minetest (after 5.4.0): Debug coordinates will no longer be "free". This means, unprivileged (!) players will no longer get to see their coordinates in the debug screen. In fact, ALL gameplay-relevant info will be hidden.
Currently, in 5.4.0, everyone can see their coordinates for "free" by pressing the debug key (F5). This is a problem for game designers since it is impossible to disable this or want to do a different method for players to reveal the coordinates. The only way to work around this is to tell players "Never press F5" or "F5 is a cheat", but this really sucks.
With the change, an unprivileged player will no longer see the coordinates and some other gameplay-relevant info in the debug screen. The basic debug screen will only contain basic debug info like FPS, draw time, RTT.
Don't worry, the full debug screen is still there. To get it (and the coordinates) back, players need to have the "basic_debug" privilege. In singleplayer, you'll get it with a "/grantme basic_debug" in chat. This might be considered a cheat in some games.
The reason for this change is that free coordinates in the debug screen give a gameplay advantage for every player that games can't get rid of. For some more complicated games, the debug coordinates can even be outright misleading. The second reason is that the debug screen is supposed to be only for debugging. Gameplay info and debug info should be fully separated. That's what the basic_debug privilege does: If you don't have it, all gameplay-relevant info is hidden in the debug screen.
For games makers that make games in which coordinates/position are important, I recommend to add HUD elements that expose the coordinates manually and maybe an item/tool/button to turn this HUD on and off. Do NOT rely on the debug screen to do that for you, as the debug screen was never meant to be abused this way in the first place. Also, the debug screen is subject to changes anyway.