IMO 0 is the best default, because if it were > 0 then mappers would
have no way to configure a door that doesn't deal any damage when blocked.
The implemented default has been 0 since (at least) Nexuiz 2.5.2 so
changing it now would not be ideal for compatibility.
The comment about the default of 2 was inherited from Quake.
"speed" movement speed (100 default)
"wait" wait before returning (3 default, -1 = never return)
"lip" lip remaining at end of move (8 default)
-"dmg" damage to inflict when blocked (2 default)
+"dmg" damage to inflict when blocked (0 default)
"sounds"
0) no sound
1) stone