bip3: Improve compatibility section

Author: murchandamus

bip-0003.md

@@ -527,9 +527,10 @@ mentioned in the [Changelog](#changelog) section.
   - The remaining statuses are Draft, Complete, Deployed, and Closed.
 - The comment system is abolished.[^comments]
 - A BIP in Draft or Complete status may no longer be closed solely on grounds of not making progress for three years.[^rejection]
-  - A BIP in Draft status may be set to Closed by anyone if it appears to have stopped making progress for at least a
-    year and its authors do not assert that they are still working on it when contacted.
+  - A BIP in Draft status may be updated to Closed status if it appears to have stopped making progress for at least a
+    year and its authors do not assert within four weeks of being contacted that they are still working on it.
   - Complete BIPs can only be moved to Closed by its authors and may remain in Complete indefinitely.
+- A Changelog section is introduced to track significant changes to BIPs after they have reached the Complete status.
 - Process BIPs are living documents that do not ossify and may be modified indefinitely.
 - Some judgment calls previously required from BIP Editors are reassigned either to the BIP authors or the repository’s
   audience.
@@ -552,6 +553,7 @@ mentioned in the [Changelog](#changelog) section.
 - "Comments-URI" and "Comment-Summary" headers are dropped from the preamble.[^comments]
 - The "Superseded-By" header is replaced with the "Proposed-Replacement" header.
 - The "Post-History" header is replaced with the "Discussion" header.
+- The optional "Version" header is introduced.
 - The "Discussions-To" header is dropped as it has never been used in any BIP.
 - Introduce Deputies and optional "Deputies" header.
 - The BIP "Title" header may now contain up to 50 characters (increased from 44 in BIP 2).