diff --git a/hledger-lib/Hledger/Data/Amount.hs b/hledger-lib/Hledger/Data/Amount.hs
index 775c06bca..05da2e52f 100644
--- a/hledger-lib/Hledger/Data/Amount.hs
+++ b/hledger-lib/Hledger/Data/Amount.hs
@@ -197,6 +197,7 @@ quoteCommoditySymbolIfNeeded s
 
 
 -- | Options for the display of Amount and MixedAmount.
+-- (See also Types.AmountStyle)
 data AmountDisplayOpts = AmountDisplayOpts
   { displayPrice         :: Bool       -- ^ Whether to display the Price of an Amount.
   , displayZeroCommodity :: Bool       -- ^ If the Amount rounds to 0, whether to display its commodity string.
@@ -420,7 +421,7 @@ showAmountPriceDebug (Just (TotalPrice pa)) = " @@ " ++ showAmountDebug pa
 -- | Given a map of standard commodity display styles, apply the
 -- appropriate one to this amount. If there's no standard style for
 -- this amount's commodity, return the amount unchanged.
--- Also apply the style to the price (except for precision)
+-- Also apply the style, except for precision, to the cost.
 styleAmount :: M.Map CommoditySymbol AmountStyle -> Amount -> Amount
 styleAmount styles a = styledAmount{aprice = stylePrice styles (aprice styledAmount)}
   where
@@ -806,8 +807,8 @@ mixedAmountCost (Mixed ma) =
 --     where a' = mixedAmountStripPrices a
 --           b' = mixedAmountStripPrices b
 
--- | Given a map of standard commodity display styles, apply the
--- appropriate one to each individual amount.
+-- | Given a map of standard commodity display styles, find and apply
+-- the appropriate style to each individual amount.
 styleMixedAmount :: M.Map CommoditySymbol AmountStyle -> MixedAmount -> MixedAmount
 styleMixedAmount styles = mapMixedAmountUnsafe (styleAmount styles)
 
diff --git a/hledger-lib/Hledger/Data/Types.hs b/hledger-lib/Hledger/Data/Types.hs
index 0b5ff6d5f..cec1e5cd2 100644
--- a/hledger-lib/Hledger/Data/Types.hs
+++ b/hledger-lib/Hledger/Data/Types.hs
@@ -250,6 +250,7 @@ data AmountPrice = UnitPrice !Amount | TotalPrice !Amount
   deriving (Eq,Ord,Generic,Show)
 
 -- | Display style for an amount.
+-- (See also Amount.AmountDisplayOpts)
 data AmountStyle = AmountStyle {
       ascommodityside   :: !Side,                   -- ^ does the symbol appear on the left or the right ?
       ascommodityspaced :: !Bool,                   -- ^ space between symbol and quantity ?
@@ -270,9 +271,10 @@ instance Show AmountStyle where
 
 -- | The "display precision" for a hledger amount, by which we mean
 -- the number of decimal digits to display to the right of the decimal mark.
--- This can be from 0 to 255 digits (the maximum supported by the Decimal library),
--- or NaturalPrecision meaning "show all significant decimal digits".
-data AmountPrecision = Precision !Word8 | NaturalPrecision deriving (Eq,Ord,Read,Show,Generic)
+data AmountPrecision =
+    Precision !Word8    -- ^ show this many decimal digits (0..255)
+  | NaturalPrecision    -- ^ show all significant decimal digits stored internally
+  deriving (Eq,Ord,Read,Show,Generic)
 
 -- | A style for displaying digit groups in the integer part of a
 -- floating point number. It consists of the character used to