Add few minor fixes.

Remove I<> that wasn't being rendered inside C<>, fix a typo, etc.

doc/Type/Signature.pod6

@@ -126,7 +126,7 @@ Please note that in the code above type constraints are enforced at two
 different levels: the first level checks if it belongs to the type in which the
 subset is based, in this case C<Int>. If it fails, a C<Type check> error is
 produced. Once that filter is cleared, the constraint that defined the subset is
-checked, producing a C<I<Constraint> type check> error if it fails.
+checked, producing a C<Constraint type check> error if it fails.
 
 X<|anonymous arguments>
 Anonymous arguments are fine too, if you don't actually need to refer to a
@@ -200,7 +200,7 @@ too. Any C<where> clause on any parameter will be executed, even if it's
 optional and not provided by the caller. In that case you may have to guard
 against undefined values within the C<where> clause.
 
-    sub f(Int $a, UInt $i? where { !$i.defined or $i > 5 } ) { ... }
+    sub f(Int $a, UInt $i? where { !$i.defined or $i > 5 }) { ... }
 
 =head3 Constraining slurpy arguments
 
@@ -255,7 +255,7 @@ and type objects (C<Int>). Consider the following code:
     #     (Str:D $: :$count!, *%_)
     #     (Str:D $: $limit, *%_)
     #     (Str:D $: *%_)»
-    say limit-lines "a \n b", Int # Always returns the max number of lines
+    say limit-lines "a \n b", Int; # Always returns the max number of lines
 
 Here we really only want to deal with string instances, not type objects. To do
 this, we can use the C<:D> type constraint.  This constraint checks that the
@@ -297,11 +297,10 @@ Here's a more practical example:
     sub can-turn-into(Str $string, Any:U $type) {
        return so $string.$type;
     }
-    say can-turn-into("3", Int);
-    say can-turn-into("6.5", Int);
-    say can-turn-into("6.5", Num);
-    say can-turn-into("a string", Num);
-    # OUTPUT: True True True False
+    say can-turn-into("3", Int);        # OUTPUT: «True␤»
+    say can-turn-into("6.5", Int);      # OUTPUT: «True␤»
+    say can-turn-into("6.5", Num);      # OUTPUT: «True␤»
+    say can-turn-into("a string", Num); # OUTPUT: «False␤»
 
 Calling C<can-turn-into> with an object instance as its second parameter
 will yield a constraint violation as intended:
@@ -331,6 +330,8 @@ known collectively as I<type smileys>:
     say Foo ~~ Any:D;    # OUTPUT: «False␤»
     say Foo ~~ Any:U;    # OUTPUT: «True␤»
     say Foo ~~ Any:_;    # OUTPUT: «True␤»
+
+    # Checking an instance of a class
     my $f = Foo.new;
     say $f  ~~ Any:D;    # OUTPUT: «True␤»
     say $f  ~~ Any:U;    # OUTPUT: «False␤»
@@ -399,7 +400,7 @@ object instance is always definite. Whether an object is a type
 object/indefinite or an object instance/definite can be verified using the
 L<DEFINITE|/language/mop#DEFINITE> (meta)method.
 
-I<Definiteness> should be distinghuished from I<definedness>, which is concerned
+I<Definiteness> should be distinguished from I<definedness>, which is concerned
 with the difference between defined and undefined objects. Whether an object is
 defined or undefined can be verified using the C<defined>-method, which is
 implemented in class L<Mu|/type/Mu>. By default a type object is considered