Overview
Glycerin is useful when the product family has water. In a moisturizer, wash, or conditioner, it can add cushion and reduce a stripped-feeling finish. In a beard oil, it is simply the wrong tool.
The tradeoff is tack. Glycerin can feel plush at low levels and sticky at higher levels, especially under facial hair. Treat it as an advanced water-phase material only in a preserved water-based formula where the water phase is measured deliberately.