I've noticed some game-play quirks in Eternity(with the "vanilla mode" box checked in the front-end) that don't happen in either Vanilla or PrBoom+. Some specific examples in Doom 1 and Doom 2:
E4M5: In vanilla, projectiles fired into the window at the very beginning of the level sometimes disappear just before collision if they're shot at an angle that brings them close to the window's edge. They always behave normally in Eternity.
E4M6: Just before getting out of the twisting passage of white rock, when the courtyard comes into view, the player will normally alert the attention of a cacodemon in the marble balcony above the lava moat. In Eternity, it won't notice you until you either get closer or shoot it.
There's also a more obvious difference in the same level, again regarding projectiles. In vanilla, shots fired into the same balcony with the cacodemon from before will disappear unless they pass through the embrasures on top. This bug never happens in Eternity, as far as I can tell.
Finally, in mission 10 of Doom 2, you can wake up some of the monsters in the blue key room if you attack near its door connected to the brown hallway towards the beginning of the level. Because of this, you'll often fight a revenant with the demons in the first few rooms. In Eternity, the revenants and arachnotrons will never wake up until you alert them within their room.
Also important is that Eternity can create and run demos with none of these discrepancies. In fact, it seems the vanilla mode option in the front-end doesn't actually function unless you're recording or playing a demo. I chose all the compatibility options manually, copying the selections under the "compatibility" and "enemies" menus while Eternity was making a vanilla demo.
I've tested this with versions 3.40.46 and 3.40.48, running on OS X 10.6.8. Is this an issue unique to me? Something I'm missing here?
