I vodka dose as well. Biofuel is essentially the same end result. In another tank that I started with, the alkalinity was 11 and always stayed there. I never saw any STN or other problems from the vodka dosing.
On my current tank, I did have some STN right around the time I started using ROX carbon and putting a large calcium reactor on line and trying to tune it in. I had never been above 9 on this tank yet had hit 11. As the alkalinity dropped and I dialed in my calcium reactor the STN began and I subsequently lost many SPS. I don't necessarily perceive a higher alkalinity being solely responsible for STN, but a downward or upward shift that isn't corrected I believe is detrimental. We read all the time that dKH should be no higher than 9 when carbon dosing. Then someone who's using a high alkalinity salt like Instant Ocean rushes to bring it down to NSW parameters and voila...their next post is about base receding and STN. It's worked both ways for me....high and low alkalinity. I think the reason many with high alkalinity see more problems is that in an SPS tank it's very difficult to keep alkalinity so high all the time, and the impending drop will cause the damage. JMO