What are the side effects of changing MySQL `character_set_server`?
You've stumbled onto one of the imponderables of MySQL's default configuration. To quote from the documentation on Character Set Configuration:


  ...when character_set_system differs from character_set_server or
  character_set_client, and you input characters manually (as database
  object identifiers, column values, or both), these may be displayed
  incorrectly in output from the client or the output itself may be
  formatted incorrectly. In such cases, starting the mysql client with
  --default-character-set=system_character_set—that is, setting the client character set to match the system character set—should fix the
  problem.


To distill, not changing the value of character_set_server will almost certainly eventually cause you problems if you use Unicode characters outside the base ISO-latin-1 character set.