Tag 667 Compatibility Option
Currently, Doomsday uses the BOOM Method of Tag 667 (ignore AASHITTY/AASTINKY/blank lower textures. Doomsday used the DOOM method of Tag 667 (Take blank lower textures and use AASHITTY/AASTINKY into consideration) in the beta-6.8 release. It was reverted back to the BOOM method in a recent build.
The BOOM method causes problems in some WADs, such as Map07 in Alien Vendetta, in which the bridge rises too high and makes the exit inaccessible without cheating.
Why not implement an option in Doomsday to toggle between the DOOM and BOOM methods of Tag 667, rather than having Doomsday use just one method? ZDoom has an option for this, called "Find shortest texture like Doom."