More tweaks from jkczyz.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

iff --git a/12-offer-encoding.md b/12-offer-encoding.md
index 8671024..1459098 100644

12-offer-encoding.md

@@ -434,9 +434,9 @@ The writer:
     - otherwise:
       - MUST NOT set `invreq_quantity`
   - otherwise (not responding to an offer):
-    - MUST set (or not set) `offer_metadata`, `offer_description`, `offer_absolute_expiry`, `offer_paths` and `offer_issuer` as it would for an offer.
+    - MUST set (or not set) `offer_description`, `offer_absolute_expiry`, `offer_paths` and `offer_issuer` as it would for an offer.
     - MUST set `invreq_payer_id` as it would set `offer_node_id` for an offer.
-    - MUST NOT include `signature`, `offer_chains`, `offer_amount`, `offer_currency`, `offer_features`, `offer_quantity_max` or `offer_node_id`
+    - MUST NOT include `signature`, `offer_metadata`, `offer_chains`, `offer_amount`, `offer_currency`, `offer_features`, `offer_quantity_max` or `offer_node_id`
     - if the chain for the invoice is not solely bitcoin:
       - MUST specify `invreq_chain` the offer is valid for.
     - MUST set `invreq_amount`.
@@ -644,7 +644,7 @@ may (due to capacity limits on a single channel) require it.
 
 A writer of an invoice:
   - MUST set `invoice_created_at` to the number of seconds since Midnight 1
-    January 1970, UTC when the offer was created.
+    January 1970, UTC when the invoice was created.
   - MUST set `invoice_amount` to the minimum amount it will accept, in units of 
     the minimal lightning-payable unit (e.g. milli-satoshis for bitcoin) for
     `invreq_chain`.
@@ -723,12 +723,13 @@ A reader of an invoice:
     - MUST reject the invoice if `invreq_payer_id` is present.
     - MUST reject the invoice if `offer_description` is not present.
   - MUST reject the invoice if `signature` is not a valid signature using `invoice_node_id` as described in [Signature Calculation](#signature-calculation).
+  - SHOULD prefer to use earlier `invoice_paths` over later ones if it has no other reason for preference.
   - if `invoice_features` contains the MPP/compulsory bit:
-    - SHOULD pay the invoice via multiple separate blinded paths.
+    - MUST pay the invoice via multiple separate blinded paths.
   - otherwise, if `invoice_features` contains the MPP/optional bit:
     - MAY pay the invoice via multiple separate payments.
   - otherwise:
-    - MUST NOT use multiple payments to pay the invoice.
+    - MUST NOT use multiple parts to pay the invoice.
   - SHOULD confirm authorization if `invoice_amount`.`msat` is not within the amount range authorized.
   - for the bitcoin chain, if the invoice specifies `invoice_fallbacks`:
     - MUST ignore any `fallback_address` for which `version` is greater than 16.