Add clarifying comments to fee estimation

src/policy/fees.cpp

@@ -281,6 +281,11 @@ void TxConfirmStats::removeTx(unsigned int entryHeight, unsigned int nBestSeenHe
     }
 }
 
+// This function is called from CTxMemPool::removeUnchecked to ensure
+// txs removed from the mempool for any reason are no longer
+// tracked. Txs that were part of a block have already been removed in
+// processBlockTx to ensure they are never double tracked, but it is
+// of no harm to try to remove them again.
 bool CBlockPolicyEstimator::removeTx(uint256 hash)
 {
     std::map<uint256, TxStatsInfo>::iterator pos = mapMemPoolTxs.find(hash);

src/validation.h

@@ -130,7 +130,7 @@ static const int64_t BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 500000;
 static const unsigned int DEFAULT_LIMITFREERELAY = 0;
 static const bool DEFAULT_RELAYPRIORITY = true;
 static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
-/** Maximum age of our tip for us to be considered current for fee estimation */
+/** Maximum age of our tip in seconds for us to be considered current for fee estimation */
 static const int64_t MAX_FEE_ESTIMATION_TIP_AGE = 3 * 60 * 60;
 
 /** Default for -permitbaremultisig */