core/txpool/legacypool: add note about pool behavior w.r.t. authorizations

core/txpool/legacypool/legacypool.go

@@ -197,6 +197,19 @@ func (config *Config) sanitize() Config {
 // The pool separates processable transactions (which can be applied to the
 // current state) and future transactions. Transactions move between those
 // two states over time as they are received and processed.
+//
+// In addition to tracking transactions, the pool will also track pending set
+// code authorizations. This helps minimize number of transactions that can be
+// trivially churned in the pool. As a standard rule, any account with a
+// deployed delegation or an in-flight authorization to deploy a delegation will
+// only be allowed a single transaction slot instead of the standard number.
+// This is due to the possibility of the account being sweeped by an unrelated
+// account. Because SetCode transactions can have many authorizations included,
+// we avoid explicitly checking their validity to save the state lookup. So long
+// as the encompassing transaction is valid, the authorization will be accepted
+// and tracked by the pool. In case the pool is tracking a pending / queued
+// transaction from a specific account, it will reject new transactions with
+// delegations from that account with standard in-flight transactions.
 type LegacyPool struct {
 	config      Config
 	chainconfig *params.ChainConfig