diff --git a/hydra-node/src/Hydra/HeadLogic.hs b/hydra-node/src/Hydra/HeadLogic.hs
index 037d54c2db7..d8dcfd09f3e 100644
--- a/hydra-node/src/Hydra/HeadLogic.hs
+++ b/hydra-node/src/Hydra/HeadLogic.hs
@@ -928,7 +928,7 @@ onOpenChainCloseTx openState newChainState closedSnapshotNumber contestationDead
     if number (getSnapshot confirmedSnapshot) > closedSnapshotNumber
       then
         outcome
-          -- TODO: As we use 'version' in the contest here, this is implies
+          -- XXX: As we use 'version' in the contest here, this is implies
           -- that our last 'confirmedSnapshot' must match version or
           -- version-1. Assert this fact?
           -- Spec: η ← combine(̅S.𝑈)
@@ -977,7 +977,7 @@ onClosedChainContestTx closedState newChainState snapshotNumber contestationDead
       | -- Spec: if ̅S.s > sc
         number (getSnapshot confirmedSnapshot) > snapshotNumber ->
           cause notifyClients
-            -- TODO: As we use 'version' in the contest here, this is implies
+            -- XXX: As we use 'version' in the contest here, this is implies
             -- that our last 'confirmedSnapshot' must match version or
             -- version-1. Assert this fact?
             -- Spec: η ← combine(̅S.𝑈)
diff --git a/hydra-node/test/Hydra/BehaviorSpec.hs b/hydra-node/test/Hydra/BehaviorSpec.hs
index 83e6f832a9d..a14e5c1f05a 100644
--- a/hydra-node/test/Hydra/BehaviorSpec.hs
+++ b/hydra-node/test/Hydra/BehaviorSpec.hs
@@ -437,7 +437,6 @@ spec = parallel $ do
                 waitUntil [n1, n2] $ DecommitApproved{headId = testHeadId, decommitTxId = txId decommitTx2, utxoToDecommit = utxoRefs [22]}
                 waitUntil [n1, n2] $ DecommitFinalized{headId = testHeadId, decommitTxId = txId decommitTx2}
 
-    -- TODO: Add it "can contest with decommit in flight"
     it "can close with decommit in flight" $
       shouldRunInSim $ do
         withSimulatedChainAndNetwork $ \chain ->
diff --git a/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseCurrent.hs b/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseCurrent.hs
index 73cb104d542..c77aeba9d6c 100644
--- a/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseCurrent.hs
+++ b/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseCurrent.hs
@@ -199,11 +199,6 @@ data CloseMutation
     MutateContestationPeriod
   deriving stock (Generic, Show, Enum, Bounded)
 
--- TODO: Add mutations which work "this way" around now. For example, before
--- we did mutate a close with signed snapshot to result in snapshot number 0,
--- which would trigger the validator. However, that would not be a faithful
--- representation of an "attack" anymore. Now, the tx creator needs to claim
--- what situation we are in now and how the snapshot signature is valid.
 genCloseCurrentMutation :: (Tx, UTxO) -> Gen SomeMutation
 genCloseCurrentMutation (tx, _utxo) =
   oneof
diff --git a/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseOutdated.hs b/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseOutdated.hs
index 7565f6c17e7..ccfb5e89bdc 100644
--- a/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseOutdated.hs
+++ b/hydra-node/test/Hydra/Chain/Direct/Contract/Close/CloseOutdated.hs
@@ -220,11 +220,6 @@ data CloseMutation
     MutateContestationPeriod
   deriving stock (Generic, Show, Enum, Bounded)
 
--- TODO: Add mutations which work "this way" around now. For example, before
--- we did mutate a close with signed snapshot to result in snapshot number 0,
--- which would trigger the validator. However, that would not be a faithful
--- representation of an "attack" anymore. Now, the tx creator needs to claim
--- what situation we are in now and how the snapshot signature is valid.
 genCloseOutdatedMutation :: (Tx, UTxO) -> Gen SomeMutation
 genCloseOutdatedMutation (tx, _utxo) =
   oneof
diff --git a/hydra-node/test/Hydra/Chain/Direct/TxTraceSpec.hs b/hydra-node/test/Hydra/Chain/Direct/TxTraceSpec.hs
index e15e50d9337..dd580464ff1 100644
--- a/hydra-node/test/Hydra/Chain/Direct/TxTraceSpec.hs
+++ b/hydra-node/test/Hydra/Chain/Direct/TxTraceSpec.hs
@@ -288,7 +288,7 @@ instance StateModel Model where
                     snapshot <- genSnapshot
                     pure $ Some Decrement{actor, snapshot}
                  )
-               | -- XXX: We dont want to generate decrements if there is nothing in the head.
+               | -- We dont want to generate decrements if there is nothing in the head.
                not (null utxoInHead)
                ]
       Closed{} ->
@@ -389,9 +389,9 @@ instance StateModel Model where
     Decrement{snapshot} ->
       headState == Open
         && snapshot.version == currentVersion
-        -- XXX: you are decrementing from existing utxo in the head
+        -- you are decrementing from existing utxo in the head
         && all (`elem` Map.keys utxoInHead) (Map.keys (decommitUTxO snapshot) <> Map.keys (snapshotUTxO snapshot))
-        -- XXX: your tx is balanced with the utxo in the head
+        -- your tx is balanced with the utxo in the head
         && sum (decommitUTxO snapshot) + sum (snapshotUTxO snapshot) == sum utxoInHead
         && (not . null $ decommitUTxO snapshot)
     Close{snapshot} ->
@@ -402,9 +402,9 @@ instance StateModel Model where
                 snapshot.number >= latestSnapshot
                   && snapshot.version `elem` (currentVersion : [currentVersion - 1 | currentVersion > 0])
            )
-        -- XXX: you are decrementing from existing utxo in the head
+        -- you are decrementing from existing utxo in the head
         && all (`elem` Map.keys utxoInHead) (Map.keys (decommitUTxO snapshot) <> Map.keys (snapshotUTxO snapshot))
-        -- XXX: your tx is balanced with the utxo in the head
+        -- your tx is balanced with the utxo in the head
         && sum (decommitUTxO snapshot) + sum (snapshotUTxO snapshot) == sum utxoInHead
      where
       Model{utxoInHead = initialUTxOInHead} = initialState
@@ -413,9 +413,9 @@ instance StateModel Model where
         && actor `notElem` alreadyContested
         && snapshot.version `elem` (currentVersion : [currentVersion - 1 | currentVersion > 0])
         && snapshot.number > latestSnapshot
-        -- XXX: you are decrementing from existing utxo in the head
+        -- you are decrementing from existing utxo in the head
         && all (`elem` Map.keys utxoInHead) (Map.keys (decommitUTxO snapshot) <> Map.keys (snapshotUTxO snapshot))
-        -- XXX: your tx is balanced with the utxo in the head
+        -- your tx is balanced with the utxo in the head
         && sum (decommitUTxO snapshot) + sum (snapshotUTxO snapshot) == sum utxoInHead
     Fanout{utxo, deltaUTxO} ->
       headState == Closed
@@ -433,35 +433,33 @@ instance StateModel Model where
     Decrement{snapshot} ->
       headState == Open
         && snapshot.version /= currentVersion
-        -- XXX: Ignore unbalanced decrements.
+        -- Ignore unbalanced decrements.
         -- TODO: make them fail gracefully and test this?
         && sum (decommitUTxO snapshot) + sum (snapshotUTxO snapshot) == sum utxoInHead
-        -- XXX: Ignore decrements that work with non existing utxo in the head
+        -- Ignore decrements that work with non existing utxo in the head
         && all (`elem` Map.keys utxoInHead) (Map.keys (decommitUTxO snapshot) <> Map.keys (snapshotUTxO snapshot))
-        -- XXX: Ignore decrement without something to decommit
+        -- Ignore decrement without something to decommit
         && (not . null $ decommitUTxO snapshot)
     Close{snapshot} ->
       headState == Open
         && ( snapshot.number == 0
               || snapshot.version `elem` (currentVersion : [currentVersion - 1 | currentVersion > 0])
            )
-        -- XXX: Ignore unbalanced close.
+        -- Ignore unbalanced close.
         -- TODO: make them fail gracefully and test this?
         && sum (decommitUTxO snapshot) + sum (snapshotUTxO snapshot) == sum utxoInHead
-        -- XXX: Ignore close that work with non existing utxo in the head
+        -- Ignore close that work with non existing utxo in the head
         && all (`elem` Map.keys utxoInHead) (Map.keys (decommitUTxO snapshot) <> Map.keys (snapshotUTxO snapshot))
     Contest{snapshot} ->
       headState == Closed
-        -- XXX: Ignore unbalanced close.
+        -- Ignore unbalanced close.
         -- TODO: make them fail gracefully and test this?
         && sum (decommitUTxO snapshot) + sum (snapshotUTxO snapshot) == sum utxoInHead
-        -- XXX: Ignore close that work with non existing utxo in the head
+        -- Ignore close that work with non existing utxo in the head
         && all (`elem` Map.keys utxoInHead) (Map.keys (decommitUTxO snapshot) <> Map.keys (snapshotUTxO snapshot))
     Fanout{} ->
       headState == Closed
 
-  -- XXX: Ignore fanouts which does not preserve the closing head
-
   nextState :: Model -> Action Model a -> Var a -> Model
   nextState m@Model{currentVersion} t _result =
     case t of
@@ -774,7 +772,7 @@ newFanoutTx actor utxo deltaUTxO = do
       spendableUTxO
       Fixture.testSeedInput
       (realWorldModelUTxO utxo)
-      -- XXX: Model world has no 'Maybe ModelUTxO', but real world does.
+      -- Model world has no 'Maybe ModelUTxO', but real world does.
       (if null deltaUTxO then Nothing else Just $ realWorldModelUTxO deltaUTxO)
       deadline
  where