Hi @lucien,
If your settings are (exactly!)…
[i18n]
client_charset = utf-8
connection_charset = utf8
database_charset = utf8
…then your OJS character set configuration is correct. Have you turned on persistent connections? If so, turn that off – your old configuration might still affect your connection pool.
These settings should correspond to the same ones you used on your old OJS installation. If not, you may have to convert your database somehow.
Regards,
Alec Smecher
Public Knowledge Project Team