doc: apply suggestions

doc/manual/src/release-notes/rl-next.md

@@ -23,16 +23,16 @@
 - Introduce a new [`outputOf`](@docroot@/language/builtins.md#builtins-outputOf) builtin.
   It is part of the [`dynamic-derivations`](@docroot@/contributing/experimental-features.md#xp-feature-dynamic-derivations) experimental feature.
 
-- The experimental nix command is now a `#!-interpreter` by appending the
-  contents of any `#! nix` lines and the script's location to a single call.
+- The experimental `nix` command is now a `#!-interpreter` by concatenating the
+  contents of any `#! nix` lines and the script's location into a single call.
 
   Verbatim strings may be passed in double backtick (```` `` ````) quotes.
   `--file` and `--expr` resolve relative paths based on the script location.
 
   Some examples:
   ```
   #!/usr/bin/env nix
-  #! nix shell --file ``<nixpkgs>`` hello --command bash
+  #! nix shell --file ``<nixpkgs>`` hello cowsay --command bash
 
   hello | cowsay
   ```

src/nix/shell.md

@@ -59,17 +59,17 @@ done by starting the script with the following lines:
 
 ```bash
 #! /usr/bin/env nix
-#! nix shell installables --command real-interpreter
+#! nix shell <installables> --command <interpreter>
 ```
 
-where *real-interpreter* is the “real” script interpreter that will be
+where <interpreter> is the interpreter that will be
 invoked by `nix shell` after it has obtained the dependencies and
 initialised the environment, and *installables* are the attribute names of
 the dependencies in Nixpkgs.
 
-The lines starting with `#! nix` specify options (see above). Note that you
-cannot write `#! /usr/bin/env nix shell -i ...` because many operating systems
-only allow one argument in `#!` lines.
+The lines starting with `#! nix` are concatenated into a single call. Note that
+you cannot write `#! /usr/bin/env nix shell -i ...` because many operating
+systems only allow one argument in `#!` lines.
 
 For example, here is a Python script that depends on Python and the
 `prettytable` package:
@@ -120,8 +120,9 @@ terraform "$@"
 
 > **Note**
 >
-> You must use double backticks (```` `` ````) when passing a simple Nix expression
-> in a nix shell shebang.
+> You can use double backticks (```` `` ````) when passing what would usually
+> be a double-quoted string in order to support multi-line strings
+> in a nix shebang.
 
 Finally, using the merging of multiple nix shell shebangs the following
 Haskell script uses a specific branch of Nixpkgs/NixOS (the 21.11 stable