This question was asked over at Mordel's and has never seemed to be addressed here officially, so I am officially asking for an answer.
According to Void-Signature Systems rules, a Mech that move 0 hexes "imposes a +3 to hit penalty on the attacker" (TacOps, pg. 349).
According to the rules for Jump Movement, a Mech may "jump into the same hex it began the turn in, for 1 MP" generating +3 to-hit movement mode penalty, 3 heat, and imposes a +1 to hit penalty on the attacker for movement (Battletech: A Game of Armored Combat, pg. 11).
Rules as written this would appear to grant a +4 to hit penalty on the attackers if a Void equipped unit jumped 0 hexes. However, it does not appear to follow the spirit of Void-Signature System and being harder to hit for NOT moving at all.
Is this working as intended?
If not, here is my suggested errata fix: replace "A ’Mech may jump into the same hex it began the turn in, for 1 MP" with "A ’Mech may jump into the same hex it began the turn in, for 1 MP and is treated as having moved 1 hex for game purposes".
