Explain fuzz initial values.

lightningd/gossip_control.c

@@ -307,6 +307,11 @@ static void json_getroute(struct command *cmd, const char *buffer, const jsmntok
 	u64 msatoshi;
 	unsigned cltv = 9;
 	double riskfactor;
+	/* Higher fuzz means that some high-fee paths can be discounted
+	 * for an even larger value, increasing the scope for route
+	 * randomization (the higher-fee paths become more likely to
+	 * be selected) at the cost of increasing the probability of
+	 * selecting the higher-fee paths. */
 	double fuzz = 75.0;
 	u8 *seed = tal_arrz(cmd, u8, sizeof(struct siphash_seed));
 

lightningd/payalgo.c

@@ -356,6 +356,14 @@ static void json_pay(struct command *cmd,
 
 	pay->getroute_tries = 0;
 	pay->sendpay_tries = 0;
+	/* Higher fuzz increases the potential fees we will pay, since
+	 * higher fuzz makes it more likely that high-fee paths get
+	 * selected. We start with very high fuzz, but if the
+	 * returned route is too expensive for the given
+	 * `maxfeepercent` we reduce the fuzz. Starting with high
+	 * fuzz means, if the user allows high fee, we can take
+	 * advantage of that to increase randomization and
+	 * improve privacy somewhat. */
 	pay->fuzz = 0.75;
 	pay->try_parent = NULL;