[doc] update documentation for new mempoolfullrbf default

doc/bips.md

@@ -33,7 +33,7 @@ BIPs that are implemented by Bitcoin Core:
 * [`BIP 111`](https://github.com/bitcoin/bips/blob/master/bip-0111.mediawiki): `NODE_BLOOM` service bit added, and enforced for all peer versions as of **v0.13.0** ([PR #6579](https://github.com/bitcoin/bitcoin/pull/6579) and [PR #6641](https://github.com/bitcoin/bitcoin/pull/6641)).
 * [`BIP 112`](https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki): The CHECKSEQUENCEVERIFY opcode has been implemented since **v0.12.1** ([PR #7524](https://github.com/bitcoin/bitcoin/pull/7524)), and has been *buried* since **v0.19.0** ([PR #16060](https://github.com/bitcoin/bitcoin/pull/16060)).
 * [`BIP 113`](https://github.com/bitcoin/bips/blob/master/bip-0113.mediawiki): Median time past lock-time calculations have been implemented since **v0.12.1** ([PR #6566](https://github.com/bitcoin/bitcoin/pull/6566)), and has been *buried* since **v0.19.0** ([PR #16060](https://github.com/bitcoin/bitcoin/pull/16060)).
-* [`BIP 125`](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki): Opt-in full replace-by-fee signaling partially implemented. See doc/policy/mempool-replacements.md.
+* [`BIP 125`](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki): Opt-in full replace-by-fee partially implemented: signaling is enforced if configured. For other replacement rules, see doc/policy/mempool-replacements.md.
 * [`BIP 130`](https://github.com/bitcoin/bips/blob/master/bip-0130.mediawiki): direct headers announcement is negotiated with peer versions `>=70012` as of **v0.12.0** ([PR 6494](https://github.com/bitcoin/bitcoin/pull/6494)).
 * [`BIP 133`](https://github.com/bitcoin/bips/blob/master/bip-0133.mediawiki): feefilter messages are respected and sent for peer versions `>=70013` as of **v0.13.0** ([PR 7542](https://github.com/bitcoin/bitcoin/pull/7542)).
 * [`BIP 141`](https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki): Segregated Witness (Consensus Layer) as of **v0.13.0** ([PR 8149](https://github.com/bitcoin/bitcoin/pull/8149)), defined for mainnet as of **v0.13.1** ([PR 8937](https://github.com/bitcoin/bitcoin/pull/8937)), and *buried* since **v0.19.0** ([PR #16060](https://github.com/bitcoin/bitcoin/pull/16060)).

doc/policy/mempool-replacements.md

@@ -10,14 +10,12 @@ A transaction ("replacement transaction") may replace its directly conflicting t
 their in-mempool descendants (together, "original transactions") if, in addition to passing all
 other consensus and policy rules, each of the following conditions are met:
 
-1. The directly conflicting transactions all signal replaceability explicitly. A transaction is
+1. If `-mempoolfullrbf=0` (the value is 1 by default), the directly conflicting transactions all signal replaceability explicitly. A transaction is
    signaling BIP125 replaceability if any of its inputs have an nSequence number less than (0xffffffff - 1).
    A transaction also signals replaceability if its version field is set to 3.
 
    *Rationale*: See [BIP125
    explanation](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki#motivation).
-   Use the (`-mempoolfullrbf`) configuration option to allow transaction replacement without enforcement of the
-   opt-in signaling rule.
 
 2. The replacement transaction only include an unconfirmed input if that input was included in
    one of the directly conflicting transactions. An unconfirmed input spends an output from a
@@ -80,3 +78,5 @@ This set of rules is similar but distinct from BIP125.
 
 * Full replace-by-fee enabled as a configurable mempool policy as of **v24.0** ([PR
   #25353](https://github.com/bitcoin/bitcoin/pull/25353)).
+
+* Full replace-by-fee is the default policy as of **v28.0** ([PR #30493](https://github.com/bitcoin/bitcoin/pull/30493)).

doc/policy/packages.md

@@ -38,7 +38,7 @@ The following rules are enforced for all packages:
 
 * Only limited package replacements are currently considered. (#28984)
 
-   - All direct conflicts must signal replacement (or the node must have `-mempoolfullrbf=1` set).
+   - If `-mempoolfullrbf=0` (the value is 1 by default), all direct conflicts must signal replacement.
 
    - Packages are 1-parent-1-child, with no in-mempool ancestors of the package.