Original text:
1. <del> The version-invariant properties of QUIC INV define a Version Negotiation packet but do not specify how an endpoint reacts when it receives one.  QUIC version 1 QUIC allows the server to use a Version Negotiation packet to indicate that the version the client chose is unacceptable, but doesn't allow the client to safely make use of that information to create a new connection with a mutually supported version. </del>  With proper safety mechanisms in place, the Version Negotiation packet can be part of a mechanism to allow two QUIC implementations The client initiates a QUIC connection by choosing an initial version and sending a first flight of QUIC packets with a long header to the <del> server INV.  The client's first flight includes Version Information (see vers-info) which will be used to optionally enable compatible version negotation (see compat-vn), and to prevent version downgrade attacks (see downgrade). </del>  Upon receiving this first flight, the server verifies whether it knows how to parse first flights from the original version.  If it Clients will ignore a Version Negotiation packet if it contains the original version attempted by the client.  The client also ignores a Version Negotiation packet that contains incorrect connection ID <del> fields; see INV. </del>  Upon receiving the Version Negotiation packet, the client will search for a version it supports in the list provided by the server.  If it 2.4. <del> QUIC connections are shared state between a client and a server INV. The compatible version negotiation mechanism defined in this document (see compat-vn) is performed as part of a single QUIC connection; that is, the packets with the client's chosen version are part of the same connection as the packets with the negotiated version. </del>  In comparison, the incompatible version negotiation mechanism, which leverages QUIC Version Negotiation packets (see incompat-vn)

Reviewer comments:
editorial nit: for consitency with RFC 9000, consider changing you reference name from [INV] -> [QUIC-INVARIANTS]

Revised text:
1.  <ins> The version-invariant properties of QUIC QUIC-INVARIANTS define a Version Negotiation packet but do not specify how an endpoint reacts when it receives one.  QUIC version 1 QUIC allows the server to use a Version Negotiation packet to indicate that the version the client chose is unacceptable, but doesn't allow the client to safely make use of that information to create a new connection with a mutually supported version. </ins> With proper safety mechanisms in place, the Version Negotiation packet can be part of a mechanism to allow two QUIC implementations The client initiates a QUIC connection by choosing an initial version and sending a first flight of QUIC packets with a long header to the  <ins> server QUIC-INVARIANTS.  The client's first flight includes Version Information (see vers-info) which will be used to optionally enable compatible version negotation (see compat-vn), and to prevent version downgrade attacks (see downgrade). </ins> Upon receiving this first flight, the server verifies whether it knows how to parse first flights from the original version.  If it Clients will ignore a Version Negotiation packet if it contains the original version attempted by the client.  The client also ignores a Version Negotiation packet that contains incorrect connection ID  <ins> fields; see QUIC-INVARIANTS. </ins> Upon receiving the Version Negotiation packet, the client will search for a version it supports in the list provided by the server.  If it 2.4.  <ins> QUIC connections are shared state between a client and a server QUIC- INVARIANTS.  The compatible version negotiation mechanism defined in this document (see compat-vn) is performed as part of a single QUIC connection; that is, the packets with the client's chosen version are part of the same connection as the packets with the negotiated version. </ins> In comparison, the incompatible version negotiation mechanism, which leverages QUIC Version Negotiation packets (see incompat-vn)