And by the way, the concept of "personal firewall" borrowed from Windows does not make any sense. Why are blocked ports opened in the first place?
Let's assume for instance avahi is a security risk that Fedora blocks: then why is it listening to the network it in the first place? This is bordering on stupidity.
Security's worst enemy is useless complexity and "personal firewalls" are exactly that: a failure to keep it simple.
Firewalls are of course useful in some complex network configurations where... "default rules" are very unlikely to make any sense either and where a real network administrator is required.