Some extra comments

src/wallet.cpp

@@ -289,6 +289,9 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn)
     return true;
 }
 
+// Add a transaction to the wallet, or update it.
+// pblock is optional, but should be provided if the transaction is known to be in a block.
+// If fUpdate is true, existing transactions will be updated.
 bool CWallet::AddToWalletIfInvolvingMe(const CTransaction& tx, const CBlock* pblock, bool fUpdate)
 {
     uint256 hash = tx.GetHash();
@@ -551,6 +554,9 @@ bool CWalletTx::WriteToDisk()
     return CWalletDB(pwallet->strWalletFile).WriteTx(GetHash(), *this);
 }
 
+// Scan the block chain (starting in pindexStart) for transactions
+// from or to us. If fUpdate is true, found transactions that already
+// exist in the wallet will be updated.
 int CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate)
 {
     int ret = 0;