> You need to escape them with commas. Ah, I overlooked that because I did not check the manual whether leading stars are escaped automatically and just assumed it, sorry. Thanks a lot!
Though, there is one minor thing I noticed: Leading stars are valid comment symbols in Fortran, as long as they are the first character in the line. They are recognized in SRC fortran blocks when the star is unescaped, but not when the star is escaped, meaning #+BEGIN_SRC fortran ,******************************* ,* a valid comment ,****************************** #+END_SRC is displayed with the org-block face instead of the usual font-lock-comment-face.