diff --git a/R/superseded-map-df.R b/R/superseded-map-df.R
index 065aa9c9..8b9fb0d1 100644
--- a/R/superseded-map-df.R
+++ b/R/superseded-map-df.R
@@ -41,6 +41,23 @@
 #'   map(\(mod) as.data.frame(t(as.matrix(coef(mod))))) |>
 #'   list_rbind()
 #'
+#' # for certain pathological inputs `map_dfr()` and `map_dfc()` actually
+#' # both combine the list by column
+#' df <- data.frame(
+#'   x = c(" 13", "  15 "),
+#'   y = c("  34",  " 67 ")
+#' )
+#'
+#' # Was:
+#' map_dfr(df, trimws)
+#' map_dfc(df, trimws)
+#'
+#' # But list_rbind()/list_cbind() fail because they require data frame inputs
+#' try(map(df, trimws) |> list_rbind())
+#'
+#' # Instead, use modify() to apply a function to each column of a data frame
+#' modify(df, trimws)
+#'
 #' # map2 ---------------------------------------------
 #'
 #' ex_fun <- function(arg1, arg2){
diff --git a/man/map_dfr.Rd b/man/map_dfr.Rd
index 3274f223..f9c9dd43 100644
--- a/man/map_dfr.Rd
+++ b/man/map_dfr.Rd
@@ -71,6 +71,23 @@ mtcars |>
   map(\(mod) as.data.frame(t(as.matrix(coef(mod))))) |>
   list_rbind()
 
+# for certain pathological inputs `map_dfr()` and `map_dfc()` actually
+# both combine the list by column
+df <- data.frame(
+  x = c(" 13", "  15 "),
+  y = c("  34",  " 67 ")
+)
+
+# Was:
+map_dfr(df, trimws)
+map_dfc(df, trimws)
+
+# But list_rbind()/list_cbind() fail because they require data frame inputs
+try(map(df, trimws) |> list_rbind())
+
+# Instead, use modify() to apply a function to each column of a data frame
+modify(df, trimws)
+
 # map2 ---------------------------------------------
 
 ex_fun <- function(arg1, arg2){