bip3: Explain why the Replaces header is unchanged

Author: murchandamus

bip-0003.md

@@ -159,7 +159,7 @@ appear in the following order. Headers marked with "\*" are optional. All other
 * Version — The current version number of this BIP. See the [Changelog](#changelog) section below.
 * Requires — A list of existing BIPs the new proposal depends on. If multiple BIPs
   are required, they should be listed in one line separated by a comma and space (e.g., "1, 2").
-* Replaces — BIP authors may place the numbers of one or more prior BIPs in the Replaces header to recommend that their
+* Replaces[^proposes-to-replace] — BIP authors may put the numbers of one or more prior BIPs in the Replaces header to recommend that their
   BIP succeeds, supersedes, or renders obsolete those prior BIPs.
 * Proposed-Replacement[^superseded-by-proposed-replacement] — When a later BIP indicates that it intends to supersede an
   existing BIP, the later BIP’s number is added to the Proposed-Replacement header of the existing BIP to indicate the
@@ -704,6 +704,16 @@ feedback, and helpful comments.
     the original BIP, the authors of the new BIP, the editors, or the community? This is addressed by making the
     "Replaces" header part of the recommendation of the authors of the new document, and replacing the "Superseded-By"
     header with the "Proposed-Replacement" header that lists any proposals that recommend replacing the original document.
+[^proposes-to-replace]: **Why was "Replaces" retained instead of changing it to "Proposes-to-Replace"?**  
+    When one BIP proposes to supersede another, it is on the original BIP where things get complicated. The BIP is an
+    author document, but depending on its progress through the workflow, it may meanwhile be co-owned by the community. Who may decide
+    whether the original document should endorse a potential replacement BIP? Is it the original authors, the authors of the new
+    proposal, the BIP Editors, some sort of community process, or a mix of all of the above?  
+    On the new BIP these problems don’t exist in the same manner. As it is freshly written, it is wholly owned by its
+    authors. The community is not yet invested and the original BIP’s authors do not have a privileged role
+    in determining the content of the new BIP. The authors of the new BIP can unilaterally recommend that it be
+    considered a replacement for a prior BIP. From there, the community can evaluate the proposal and adopt or
+    reject it, thus establishing whether it is successful in superseding the original or not.
 [^evidence]: **How is evidence for advancing to Deployed evaluated?**  
     Whether evidence is deemed convincing to move a BIP to Deployed is up to the BIP Editors and Bitcoin community.
     Running a single instance of a personal fork of a software project might be rejected, while a small software project with