As a recent returnee to ACE Mod, I can confirm that spawn-camping is an occasional problem, though not on all maps - some seem more prone to it than others and the regularity with which one is killed within seconds of spawning seems to suggest that those who have found a "sweet spot" do not realise it is on top of a spawn point. Only once, recently, have I, personally, asked a visitor to cease (no admins were playing at the time). I was poised to record a video but the map ended and he obviously had a crisis of conscience and played more fairly on the next map. (For the record it was not the complainant.)
I do doubt that the four-second spawn protection is actually active as it is common to be shot within two or three steps following the spawn.
To those that really do get irritated by being shot by such campers, I have a solution... STFU and drop some C4 on them!