Apply suggestions from code review

Co-authored-by: Dmitri Gribenko <gribozavr@gmail.com>

src/idiomatic/leveraging-the-type-system/newtype-pattern/parse-don-t-validate.md

@@ -35,7 +35,8 @@ impl Username {
 
 - The newtype pattern, combined with Rust's module and visibility system, can be
   used to _guarantee_ that instances of a given type satisfy a set of
-  invariants.\
+  invariants.
+
   In the example above, the raw `String` stored inside the `Username` struct
   can't be accessed directly from other modules or crates, since it's not marked
   as `pub` or `pub(in ...)`. Consumers of the `Username` type are forced to use
@@ -43,7 +44,7 @@ impl Username {
   ensuring that all instances of `Username` satisfy those checks.
 
 - The `as_str` method allows consumers to access the raw string representation
-  (e.g. to store it in a database) but, thanks to Rust's borrow checker, they
+  (e.g., to store it in a database) but, thanks to Rust's borrow checker, they
   can't modify it.
 
 - Stress the importance of evaluating _the entire API surface_ exposed by a

src/idiomatic/leveraging-the-type-system/newtype-pattern/semantic-confusion.md

@@ -4,8 +4,7 @@ minutes: 5
 
 # Semantic Confusion
 
-There is room for confusion whenever a function takes multiple arguments of the
-same type:
+When a function takes multiple arguments of the same type, call sites are unclear:
 
 ```rust
 # struct LoginError;
@@ -21,7 +20,7 @@ pub fn login(username: &str, password: &str) -> Result<(), LoginError> {
 login(password, username);
 ```
 
-The newtype pattern can be used to prevent this class of errors at compile time:
+The newtype pattern can prevent this class of errors at compile time:
 
 ```rust
 pub struct Username(String);
@@ -50,7 +49,7 @@ login(password, username);
 
 - Nonetheless, note that there are legitimate scenarios where a function may
   take multiple arguments of the same type. In those scenarios, if correctness
-  is of paramount important, consider using a struct with named fields as input:
+  is of paramount importance, consider using a struct with named fields as input:
   ```rust
   pub struct LoginArguments {
       pub username: &str,