Original text:
could become blocked to the value of SETTINGS_QPACK_BLOCKED_STREAMS at all times.  If a decoder encounters more blocked streams than it promised to support, it MUST treat this as a connection error of type <del> HTTP_QPACK_DECOMPRESSION_FAILED. </del>  Note that the decoder might not become blocked on every stream which risks becoming blocked. When processing header blocks, the decoder expects the Required Insert Count to exactly match the value defined in blocked-streams. If it encounters a smaller value than expected, it MUST treat this as <del> a connection error of type HTTP_QPACK_DECOMPRESSION_FAILED; see invalid-references.  If it encounters a larger value than expected, it MAY treat this as a connection error of type HTTP_QPACK_DECOMPRESSION_FAILED. </del>  2.2.2. representation to a dynamic table entry which has already been evicted or which has an absolute index greater than or equal to the declared Required Insert Count (header-prefix), it MUST treat this as <del> a connection error of type "HTTP_QPACK_DECOMPRESSION_FAILED". </del>  If the decoder encounters a reference in an encoder instruction to a dynamic table entry which has already been evicted, it MUST treat <del> this as a connection error of type "HTTP_QPACK_ENCODER_STREAM_ERROR". </del>  3. When the decoder encounters an invalid static table index in a header block representation it MUST treat this as a connection error of type <del> "HTTP_QPACK_DECOMPRESSION_FAILED".  If this index is received on the encoder stream, this MUST be treated as a connection error of type "HTTP_QPACK_ENCODER_STREAM_ERROR". </del>  3.2. then added to the table.  It is an error if the encoder attempts to add an entry that is larger than the dynamic table capacity; the decoder MUST treat this as a connection error of type <del> "HTTP_QPACK_ENCODER_STREAM_ERROR". </del>  A new entry can reference an entry in the dynamic table that will be evicted when adding this new entry into the dynamic table. send the same non-zero value in its SETTINGS frame.  If it specifies any other value, or omits SETTINGS_QPACK_MAX_TABLE_CAPACITY from SETTINGS, the encoder must treat this as a connection error of type <del> "HTTP_QPACK_DECODER_STREAM_ERROR". </del>  For HTTP/3 servers and HTTP/3 clients when 0-RTT is not attempted or is rejected, the maximum table capacity is 0 until the encoder value of the SETTINGS_QPACK_MAX_TABLE_CAPACITY parameter (configuration) received from the decoder.  The decoder MUST treat a new dynamic table capacity value that exceeds this limit as a <del> connection error of type "HTTP_QPACK_ENCODER_STREAM_ERROR". </del>  Reducing the dynamic table capacity can cause entries to be evicted; see eviction.  This MUST NOT cause the eviction of entries which are If an encoder receives a Header Acknowledgement instruction referring to a stream on which every header block with a non-zero Required Insert Count has already been acknowledged, that MUST be treated as a <del> connection error of type "HTTP_QPACK_DECODER_STREAM_ERROR". </del>  The Header Acknowledgement instruction might increase the Known Received Count; see known-received-count. An encoder that receives an Increment field equal to zero, or one that increases the Known Received Count beyond what the encoder has sent MUST treat this as a connection error of type <del> "HTTP_QPACK_DECODER_STREAM_ERROR". </del>  4.5. algorithm such as the following.  If the decoder encounters a value of EncodedInsertCount that could not have been produced by a conformant encoder, it MUST treat this as a connection error of type <del> "HTTP_QPACK_DECOMPRESSION_FAILED". </del>  TotalNumberOfInserts is the total number of inserts into the decoder's dynamic table.

Reviewer comments:
I noticed that the QPACK error codes still started with the HTTPQPACK prefix, while the HTTP document has shifted to H3 as the prefix. I shortened the QPACK prefix to simply "QPACK", though "H3QPACK" could work, too. Along the way, I noticed that backticks were sometimes, but not always, used when referring to the error code names. We haven't been in the HTTP document, so I reconciled them to not. Again, this could go the opposite way. I also noticed that the settings are "SETTINGSQPACK" except in the IANA registration where they're simply "QPACK". I didn't touch those, but am open to feedback on whether that's worth trimming/reconciling.
NAME I don't need your approval, but I kind of do need NAME
Well, you did ask :)
NAME could you review and potentially merge?
Do it. You don't need my approval to do something that is so self-evidently a good idea.QPACK_ prefix WFM

Revised text:
could become blocked to the value of SETTINGS_QPACK_BLOCKED_STREAMS at all times.  If a decoder encounters more blocked streams than it promised to support, it MUST treat this as a connection error of type  <ins> QPACK_DECOMPRESSION_FAILED. </ins> Note that the decoder might not become blocked on every stream which risks becoming blocked. When processing header blocks, the decoder expects the Required Insert Count to exactly match the value defined in blocked-streams. If it encounters a smaller value than expected, it MUST treat this as  <ins> a connection error of type QPACK_DECOMPRESSION_FAILED; see invalid- references.  If it encounters a larger value than expected, it MAY treat this as a connection error of type QPACK_DECOMPRESSION_FAILED. </ins> 2.2.2. representation to a dynamic table entry which has already been evicted or which has an absolute index greater than or equal to the declared Required Insert Count (header-prefix), it MUST treat this as  <ins> a connection error of type QPACK_DECOMPRESSION_FAILED. </ins> If the decoder encounters a reference in an encoder instruction to a dynamic table entry which has already been evicted, it MUST treat  <ins> this as a connection error of type QPACK_ENCODER_STREAM_ERROR. </ins> 3. When the decoder encounters an invalid static table index in a header block representation it MUST treat this as a connection error of type  <ins> QPACK_DECOMPRESSION_FAILED.  If this index is received on the encoder stream, this MUST be treated as a connection error of type QPACK_ENCODER_STREAM_ERROR. </ins> 3.2. then added to the table.  It is an error if the encoder attempts to add an entry that is larger than the dynamic table capacity; the decoder MUST treat this as a connection error of type  <ins> QPACK_ENCODER_STREAM_ERROR. </ins> A new entry can reference an entry in the dynamic table that will be evicted when adding this new entry into the dynamic table. send the same non-zero value in its SETTINGS frame.  If it specifies any other value, or omits SETTINGS_QPACK_MAX_TABLE_CAPACITY from SETTINGS, the encoder must treat this as a connection error of type  <ins> QPACK_DECODER_STREAM_ERROR. </ins> For HTTP/3 servers and HTTP/3 clients when 0-RTT is not attempted or is rejected, the maximum table capacity is 0 until the encoder value of the SETTINGS_QPACK_MAX_TABLE_CAPACITY parameter (configuration) received from the decoder.  The decoder MUST treat a new dynamic table capacity value that exceeds this limit as a  <ins> connection error of type QPACK_ENCODER_STREAM_ERROR. </ins> Reducing the dynamic table capacity can cause entries to be evicted; see eviction.  This MUST NOT cause the eviction of entries which are If an encoder receives a Header Acknowledgement instruction referring to a stream on which every header block with a non-zero Required Insert Count has already been acknowledged, that MUST be treated as a  <ins> connection error of type QPACK_DECODER_STREAM_ERROR. </ins> The Header Acknowledgement instruction might increase the Known Received Count; see known-received-count. An encoder that receives an Increment field equal to zero, or one that increases the Known Received Count beyond what the encoder has sent MUST treat this as a connection error of type  <ins> QPACK_DECODER_STREAM_ERROR. </ins> 4.5. algorithm such as the following.  If the decoder encounters a value of EncodedInsertCount that could not have been produced by a conformant encoder, it MUST treat this as a connection error of type  <ins> QPACK_DECOMPRESSION_FAILED. </ins> TotalNumberOfInserts is the total number of inserts into the decoder's dynamic table.