FavourSingleton: improve docs

Author: knocte

docs/content/how-tos/rules/FL0089.md

@@ -14,7 +14,10 @@ Rule to detect usage of lists or arrays with only one item.
 
 ## Rationale
 
-List.singleton/Array.singleton is more readable and explicit than [ foo]/[| foo |].
+`List.singleton foo`/`Array.singleton foo` is more readable and explicit than `[foo]`/`[|foo|]`.
+Especially if we take in account that F# newbies may not yet be familiar with the difference between
+inline array vs list instantiation; and square brackets with only one element could potentially be
+confused with an indexing accessor.
 
 ## How To Fix