Add missing documentation.
# type: integer
# chat_message_limit_trigger_kick = 50
+# At this distance the server will aggressively optimize which blocks are sent to clients.
+# Small values potentially improve performance a lot, at the expense of visible rendering glitches.
+# (some blocks will not be rendered under water and in caves, as well as sometimes on land)
+# Setting this to a value greater than max_block_send_distance disables this optimization.
+# Stated in mapblocks (16 nodes)
+# type: int
+# block_send_optimize_distance = 4
+
### Physics
# type: float