Add a few code comments

src/Language/Haskell/Brittany/Internal/Backend.hs

@@ -287,6 +287,8 @@ layoutBriDocM = \case
     case mDP of
       Nothing -> pure ()
       Just (y, x) ->
+        -- we abuse this, as we probably will print the KW next, which is
+        -- _not_ a comment..
         layoutMoveToCommentPos y (if shouldRestoreIndent then x else 0)
     layoutBriDocM bd
   BDNonBottomSpacing _ bd -> layoutBriDocM bd

src/Language/Haskell/Brittany/Internal/BackendUtils.hs

@@ -173,6 +173,8 @@ layoutSetCommentCol = do
   unless (Data.Maybe.isJust $ _lstate_commentCol state)
     $ mSet state { _lstate_commentCol = Just col }
 
+-- This is also used to move to non-comments in a couple of places. Seems
+-- to be harmless so far..
 layoutMoveToCommentPos
   :: ( MonadMultiWriter Text.Builder.Builder m
      , MonadMultiState LayoutState m

src/Language/Haskell/Brittany/Internal/Types.hs

@@ -88,7 +88,13 @@ data LayoutState = LayoutState
                                    -- move-to-DP at a start of a comment.
                                    -- Necessary because some keyword DPs
                                    -- are relative to the last non-comment
-                                   -- entity (for some reason)
+                                   -- entity (for some reason).
+                                   -- This is not very strictly reset to 0,
+                                   -- so we might in some cases get "artifacts"
+                                   -- from previous document elements.
+                                   -- But the worst effect at the moment would
+                                   -- be that we introduce less newlines on
+                                   -- moveToKWDP, which seems harmless enough.
   }
 
 lstate_baseY :: LayoutState -> Int