Fred adds the value 89EA443CCDA16B89 to every password as a salt. What issue might this cause?

Salt reuse is a critical mistake, because it would allow a rainbow table to be generated using that salt. Although standard rainbow tables would not work, a reused salt would only require the creation of a single new rainbow table. Alphanumeric salts are not a problem, long salts are not a problem, and this salt is a reasonable length at 16 characters using hexadecimal.