bullets shot through Doorman Portals have irregular damage falloff. Spotting an enemy through a door does not mark them.

[SuperMatter]

View attachment Deadlock Doormanning.mp4

Presumably due to how the game calculates weapon falloff (distance between the shooter and the victim), shooting through a doorman door will have the bullet deal minimum falloff damage.

Bonus: Seeing a player through a doorway will not mark them on the map, nor will it reveal their health