message: [doxygen] Actually display comment
diff: @@ -164,6 +164,7 @@ extern CFeeRate minRelayTxFee;
  /** Absolute maximum transaction fee (in satoshis) used by wallet and mempool (rejects high fee in sendrawtransaction) */
  extern CAmount maxTxFee;
  extern bool fEnableReplacement; // BU TODO is this RBF flag?
  +/** If the tip is older than this (in seconds), the node is considered to be in initial block download. */
  extern int64_t nMaxTipAge;
  /** Best header we've seen so far (used for getheaders queries' starting points). */
  