lower dowm header levels

communications_protocol.asciidoc

@@ -30,11 +30,11 @@ A Lightning Message falls into one of the following groups:
 
 Lightning Messages follows two forethoughtful rules: "it's OK to be odd" rule and "ignore additional data" rule. Both of them allow for future extension of Lightning Messages.
 
-=== "It's OK to be odd" rule
+==== "It's OK to be odd" rule
 
 Lightning Message type follows the _it's ok to be odd_ rule. A node is allowed to send a message of an _odd_-numbered type, but not _even_-numbered type without prior negotiation. Once a node receives an _oddly_-but-unknown-typed message, it should ignore it. However, if it receives an _evenly_-but-unknown-typed message, it is expected to fail the channels.
 
-=== "Ignore additional data" rule
+==== "Ignore additional data" rule
 
 The length of a Lightning Message is a 2-byte unsigned int, so the maximum message size is 65535 bytes.