this is perfectly readable, everything is compact, and different parts of the functionality
of reading each config line is grouped column-wise

...
else if (!strcmp("user",          key)) { conf.user          = remaining_line(fd); }
else if (!strcmp("password",      key)) { conf.password      = remaining_line(fd); }
else if (!strcmp("client_cert",   key)) { conf.client_cert   = remaining_line(fd); }
else if (!strcmp("client_key",    key)) { conf.client_key    = remaining_line(fd); }
else if (!strcmp("server_cert",   key)) { conf.server_cert   = remaining_line(fd); }
else if (!strcmp("f_samp_Hz",     key)) { conf.fsamp         = read_integer(fd);   }
else if (!strcmp("f_bitrate_bps", key)) { conf.bps           = read_integer(fd);   }
...

but oh no! lines too long (or imagine they are at least)!

...
else if (!strcmp("user", key)) {
	conf.user = remaining_line(fd);
}
else if (!strcmp("password", key)) {
	conf.password = remaining_line(fd);
}
else if (!strcmp("client_cert", key)) {
	conf.client_cert   = remaining_line(fd);
}
...

which is less compact and you can't get an as good overview, I've reformatted less than
half of the config reading, and I'm already using more lines