f add more color to why we care about special-casing 0

Author: TheBlueMatt

lightning/src/routing/scoring.rs

@@ -1782,7 +1782,11 @@ mod bucketed_history {
 			let mut cumulative_success_prob_times_billion = 0;
 			// Special-case the 0th min bucket - it generally means we failed a payment, so only
 			// consider the highest (i.e. largest-offset-from-max-capacity) max bucket for all
-			// points against the 0th min bucket!
+			// points against the 0th min bucket. This avoids the case where we fail to route
+			// increasingly lower values over a channel, but treat each failure as a separate
+			// datapoint, many of which may have relatively high maximum-available-liquidity
+			// values, which will result in us thinking we have some nontrivial probability of
+			// routing up to that amount.
 			if self.min_liquidity_offset_history.buckets[0] != 0 {
 				let mut highest_max_bucket_with_points = 0;
 				let mut total_max_points = 0;