We can add a permissions key for that in the next update After the update, you will be able to disable the debug light (L) by adding debuglight: false to the "general" permissions group, for example:
finally some good use for all the pretty lighting effects of torches and stuff, it really goes to waste when people have L turned on by default all the time and having to put up a sign asking to please turn it off lol.
almost sounds like "please dont push the button" and people do the opposite :p