Source points are not 'anti-fun'.
Anti-fun would be a mechanic that explicitly punishes you for doing good, or playing an alternate play-style, like the enemy scaling in Oblivion/Skyrim(gotta love a level 100 alchemist going up against the same enemies a level 100 stealth archer does).
Source points are a resource to manage.
They restrict how often you are allowed to use your strongest abilities, to further accentuate their special status.
