This bis primarily intends to address errata and also clarify the behavior of how non-transitive extended communities behave at ebgp boundaries. Procedure is addressed where non-transitive ECs can be injected across the eBGP boundary. This addresses use cases covered by things such as the link-bandwidth EC and work in BESS on https://datatracker.ietf.org/doc/html/draft-ietf-bess-ebgp-dmz
However, since this document is a foundational document to the extended community feature and there have been a number of updates to the registry procedures, the majority of text changed covers IANA considerations to make this bis an appropriate base update. Some of the procedure is intentionally deferred to the RFC 7153 document which made some of the registry chnages.
The original security considerations were known to be poor, and the security ADs have requested they be updated.