Clean up some more TODOs

Author: michaelsproul

beacon_node/store/src/hot_cold_store.rs

@@ -1483,15 +1483,15 @@ impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotColdDB<E, Hot, Cold>
                     state_slot = %state.slot(),
                     "State already exists in state cache",
                 );
-                // TODO(hdiff): do we still have issues with states being in the cache and not on
-                // disk? Maybe we need to ensure disk writes happen prior to cache inserts?
-                // return Ok(());
+                // NOTE: We used to return early here, but had some issues with states being
+                // in the cache but not on disk. Instead of relying on the cache we try loading
+                // the state summary below and rely on that instead.
             }
             PutStateOutcome::Finalized => {} // Continue to store.
         }
 
-        // TODO(hdiff): is this optimization necessary? Computing diffs is expensive so we may want
-        // to avoid it.
+        // Computing diffs is expensive so we avoid it if we already have this state stored on
+        // disk.
         if self.load_hot_state_summary(state_root)?.is_some() {
             debug!(
                 slot = %state.slot(),