You lose the penetration bonus from Tenacious because the modal has priority and still get the deflection malus obviously. So it's a lose/lose situation, better to simply turn off both sword and sabre modal, which for a martial class, is some very silly design imo.
I always supposed that weapon modals were counted as passives because, well, they are passives... But recently I discovered that the additional +2 Pen from my Sword Modal was actually suppressing the bonus penetration from my Tenacious inspiration (from Berserker's Frenzy). Now that seems very odd to begin with that modals aren't actually considered as passives and I would really like to know if this is working as intended. Also it's very counterintuitive that the sword Modwyr appears as a weapon perfectly tailored for Berserkers as it cancels the Confused status and friendly fire from C