It is said "The user may ignore the negative MOD to BS imposed by the target's Partial Cover." So target still gets -3 Damage mod? The wording of Triangulated Fire is not so clear. Do it ignore only BS mod or Damage mode as well?
Marksmanship is clear in that it explicitely says it's the MOD to BS that it ignores. As for Triangulated fire... The damage reduction from cover isn't a MOD. And I believe the reading of Triangulated Fire is that it ignores all other MODs pertaining to the "BS-3 Roll" that it mentions.
I'm afraid that the -3 to weapon damage doesn't apply in either case, since that (-3) is a MOD. On page 46 of the rulebook it is stated that cover reduces the weapon's damage on the saving throw: If the target is in Partial Cover, the attacker will apply a -3 MOD to their BS Attack Roll and the target of the BS Attack reduces the Attack Damage by 3 for Saving Roll purposes, if the Roll was necessary. And the rulebook itself, and page 28 indicates that the modification of the saving throw is a MOD: The most commonly used MODs are: ◼ Cover (see page 48): can modify the BS, PH, WIP, and Saving Rolls.
Both Marksmanship and Triangulated fire refer specifically to "BS", "BS attack" and "BS roll" though. The -3 Damage is a MOD applied to the saving roll and thus not affected by either skill.
Although not considering the effects of a skill as part of that skill does not seem very correct either.
Both skills refer to MODs to BS. The Damage MOD is not a MOD to the BS attribute but, no wonder, to the Damage attribute.
I admit that in Marksmanship it could be considered that way, yes, because it literally says «MODs to BS»; but in Triangulated Fire it doesn't say that it only applies to MODs to BS, it literally says «all other MODs" and the MOD to Damage is not a MOD to BS but it is «other MOD» that is applied during the resolution of a BS Attack, the rule even has to specify a MOD that will be applied, the MOD to Burst (which is also not a MOD to BS) because otherwise it would also be ignored.
It is referring to the BS roll. All of the example are MODs to the BS value, and the list ends with ellipsis for any other MODs to BS value that could be created in the future.
That reference is not so clear, because then saying that the MOD to B will be applied is totally unnecessary.
At some point in the previous (N3) edition one of the Marksmanship skill levels (as there were two) allowed you to effectively ignore cover, both in terms of BS and ARM rolls. This does cause some problem to the payers who still have the old rules deep in their heads (uhm... guilty...). However, the current way the rules are written is pretty clear and unambigious: BS mod due to Cover is affected - and only the BS mod.
As a cordial feedback I can tell you that assuming what others know or not of the rules and that what is clear to you is clear to others... is not usually a wise way to solve other people's doubts. On the other hand if it is so clear why expressly indicate that a MOD that has absolutely nothing to do with BS does apply?
Because it is a change from N3, IIRC. To explicit the difference from previous edition for us old grumpy player who memorized the (now wrong) rules.
Just a reminder of what Partial Cover says. If the target is in Partial Cover, the attacker will apply a -3 MOD to their BS Attack Roll and the target of the BS Attack reduces the Attack Damage by 3 for Saving Roll purposes, if the Roll was necessary. As you can see, it is written very similarly to the skills being discussed but with the Damage reduction written separately. There were three levels and I think you're thinking of the X:th level which got changed when it was pointed out that it was mathematically unsound to use it in almost all situations. Level 2 is the same as the current Marksmanship skill, word for word.
The argument that it is to explain the change in the Rules of the MODs from N3 to N4 does not seem correct to me, because it is strange that to explain that one of them does not apply, reduce the B to 1, something that the new rule does not even insinuate can be done, it is done by saying that the MODs to B are applied.