Hi.
I have seen a video of a Minetest newbie who accidently and without noticing hit the F4 key during the game session (I knew it because it was shown on his screen) and became confused since the world around him did not get (render) updates anymore. He became confused by this and thought this is a bug in Minetest. He then restarted the world and everything went to normal.
I don’t know where to find this video again but I think you get the idea.
This can be confusing and frustating for newbies. They may get frustrated because they think they see an unloaded area which never loads. They get confused because they can walk into the seemingly unloaded areas.
Probably some other newbies got confused by this, too. In my early Minetest days, it occoured to me, too.
This feature is only really useful for developers; for normal players it is most the time the opposite of useful. ;-)
I therefore suggest to remove this key-binding (not the feature!) by default and it should only work if it has been explicitly enabled in the settings. If not, pressing F4 should do nothing.
I suggest this in the name of newbie-friendlyness.