Apply suggestions from code review

Co-authored-by: Johel Ernesto Guerrero Peña <[email protected]>

Author: jensmaurer

source/compatibility.tex

@@ -48,7 +48,7 @@
 \rationale
 Enable repurposing a deprecated syntax to support multidimensional indexing.
 \effect
-Valid C++ program that uses a comma expression within a
+Valid \CppXX{} code that uses a comma expression within a
 subscript expression may fail to compile. For example:
 \begin{codeblock}
 arr[1, 2]               // was equivalent to \tcode{arr[(1, 2)]}, now equivalent to \tcode{arr.\keyword{operator}[](1, 2)} or ill-formed