pectra fees: tweaks from Seb's review

pages/notices/pectra-fees.mdx

@@ -19,24 +19,30 @@ is_imported_content: 'false'
 
 The Ethereum L1 Pectra upgrade has introduced changes to calldata gas costs via [EIP-7623](https://eips.ethereum.org/EIPS/eip-7623) that may affect OP Stack chain profitability in specific configurations and market conditions. This notice outlines the potential impact on your chain and recommends specific actions.
 
-[EIP-7623](https://eips.ethereum.org/EIPS/eip-7623) increases the amount of gas payable for calldata transactions. These include such transactions as those used by OPStack chains *before the [Ecotone upgrade](https://specs.optimism.io/protocol/ecotone/overview.html)* when blob data availability (blob DA) was introduced.
+[EIP-7623](https://eips.ethereum.org/EIPS/eip-7623) increases the amount of gas payable for calldata-heavy transactions. These include such transactions as those used by OPStack chains *before the [Ecotone upgrade](https://specs.optimism.io/protocol/ecotone/overview.html)* when blob data availability (blob DA) was introduced.
 
-Blob DA has now been the default and recommended option for the OPStack for some time, so almost all chains make use of it. In order to continue to optimize for chains operating with blob DA, the Optimism protocol's current DA fee pricing formula has remained unchanged despite Pectra activating on Ethereum.
+Blob DA has now been the default and recommended option for the OPStack for some time, so almost all chains make use of it. In order to continue to optimize for chains operating with blob DA, the Optimism protocol's current DA fee pricing formula has remained unchanged despite Pectra activating on Ethereum. This allowed us to leave the base fee scalar of modern fee configurations unchanged, because it accounts for only the fixed intrinsic gas cost of 21,000 of a blob transaction.
 
 Chains configured for blob data availability remain entirely unaffected by the Pectra upgrade. However, chains configured for calldata (i.e. operating in a legacy DA mode) may experience a reduction in profitability. It possible for such chains to be making a loss on data availabilty costs under certain market conditions. Therefore all chains should check their fee scalar config.
 
 ## Actions required
 
 Since the Ecotone upgrade, the Optimism protocol prices L2 transactions using a function that incorporates the L1 base fee as well as the L1 blob base fee. The other inputs are the so-called "Ecotone scalars": operator-controlled parameters stored in the SystemConfig contract which can be used to tune the chain's (approximate) target profit margin for DA.
 
-Please review your [Ecotone scalar chain configuration](/operators/chain-operators/management/blobs). If your chain uses a zero blob base fee scalar, meaning it's configured to price for calldata only, you may need to update the base fee scalar and or the blob base fee scalar. Otherwise, no action is necessary.
+Please review your [Ecotone scalar chain configuration](/operators/chain-operators/management/blobs). 
 
+<Callout type="info">
+If your chain uses a zero blob base fee scalar, meaning it's configured to price for calldata only, you may need to update the base fee scalar and/or the blob base fee scalar. Otherwise, no action is necessary and the rest of this section does not apply.
+</Callout>
+
+### Calldata-only chains
 If your batcher is configured to submit using calldata *only*, then you should:
 
 *   scale your base fee scalar by 10/4.
 
 This will ensure that, since you are paying exclusively for calldata DA, you are charging users appropriately such that your target profit margin is the same as it was before Pectra.
 
+### Blob DA chains
 If your batcher is configured to submit using blob DA, or configured to automatically choose the cheaper of the two DA modes, then you should adjust your Ecotone scalars for blob DA pricing (meaning a nonzero blob base fee scalar). You are referred back to [this guide](/operators/chain-operators/management/blobs). Doing so will ensure that you are charging accurately for using blob DA. Without such a change it is likely that you are overcharging users most of the time, and undercharging them in the rare occasions where blob DA is more expensive than calldata DA on Ethereum mainnet.
 
 As ever, you may continue to tweak the Ecotone scalars as desired in order to adjust the profitability of your chain.

pages/operators/chain-operators/management/blobs.mdx

@@ -122,7 +122,7 @@ blobs back to using calldata.
   information is tuned to a network like OP Mainnet.
 
   <Callout type="warning">
-  Since the Pectra upgrade on L1, chains which exclusively use calldata DA need to scale up their BaseFeeScalar by 16/10. See [this notice](/notices/pectra-fees).
+  Since the Pectra upgrade on L1, chains which exclusively use calldata DA need to scale up their BaseFeeScalar by 10/4. See [this notice](/notices/pectra-fees).
   </Callout>
 
   Chains can update their fees to increase or decrease their margin. If using calldata, then `BaseFeeScalar` should be scaled to achieve the desired margin.