doc: Update mempool_replacements.md to reflect feerate diagram checks

doc/policy/mempool-replacements.md

@@ -12,12 +12,7 @@ other consensus and policy rules, each of the following conditions are met:
 
 1. (Removed)
 
-2. The replacement transaction only include an unconfirmed input if that input was included in
+2. (Removed)
-   one of the directly conflicting transactions. An unconfirmed input spends an output from a
-   currently-unconfirmed transaction.
-
-   *Rationale*: When RBF was originally implemented, the mempool did not keep track of
-   ancestor feerates yet. This rule was suggested as a temporary restriction.
 
 3. The replacement transaction pays an absolute fee of at least the sum paid by the original
    transactions.
@@ -38,23 +33,16 @@ other consensus and policy rules, each of the following conditions are met:
    *Rationale*: Try to prevent DoS attacks where an attacker causes the network to repeatedly relay
    transactions each paying a tiny additional amount in fees, e.g. just 1 satoshi.
 
-5. The number of original transactions does not exceed 100. More precisely, the sum of all
+5. The number of distinct clusters corresponding to conflicting transactions does not exceed 100.
-   directly conflicting transactions' descendant counts (number of transactions inclusive of itself
-   and its descendants) must not exceed 100; it is possible that this overestimates the true number
-   of original transactions.
 
-   *Rationale*: Try to prevent DoS attacks where an attacker is able to easily occupy and flush out
+   *Rationale*: Limit CPU usage required to update the mempool for so many transactions being
-   significant portions of the node's mempool using replacements with multiple directly conflicting
+   removed at once.
-   transactions, each with large descendant sets.
 
-6. The replacement transaction's feerate is greater than the feerates of all directly conflicting
+6. The feerate diagram of the mempool must be strictly improved by the replacement transaction.
-   transactions.
 
-   *Rationale*: This rule was originally intended to ensure that the replacement transaction is
+   *Rationale*: This ensures that block fees in all future blocks will go up
-   preferable for block-inclusion, compared to what would be removed from the mempool. This rule
+   after the replacement (ignoring tail effects at the end of a block).
-   predates ancestor feerate-based transaction selection.
 
-This set of rules is similar but distinct from BIP125.
 
 ## History
 
@@ -79,3 +67,5 @@ This set of rules is similar but distinct from BIP125.
 * Signaling for replace-by-fee is no longer required as of [PR 30592](https://github.com/bitcoin/bitcoin/pull/30592).
 
 * The incremental relay feerate default is 0.1sat/vB ([PR #33106](https://github.com/bitcoin/bitcoin/pull/33106)).
+
+* Feerate diagram policy enabled in conjunction with switch to cluster mempool as of **v31.0**.