Sympa web pages are full UTF-8. These strange characters show that the web browser interpret them using ISO charset.
Ensure that your Apache server does not force ISO encoding with a directive like this :
AddDefaultCharset ISO-8859-1
If so, remove the AddDefaultCharset directive.
If you set up your server so that the web interfacebase URL is:
http://server/sympa
And you find URL cropped to:
http://server/lists http://server/list/sendpasswd/ etc.
instead of:
http://server/sympa/lists http://server/list/sympa/sendpasswd/ etc.
It is likely that the env_reset option of sudo was set. This option removes all environment variables, including those sent to Sympa by the web server, which indicate the base URL for all the links in the web interface.
See sudo to set up the correct sudo configuration.