Originally Posted by Andrew R Stewart

The concerns about too high a stem position is that the stem's bottom portion can see too much bending forces and can break off the upper portion of the stem, with only the wedge and bolt holding it together while you try to not lose control while descending Assuming one doesn't crash too hard that broken stem could be replaced with one that allows a taller position (like the Nitto Techmatics mentioned). Not the end of the world (for the bike...)

But the other more devious potential is that the stem lower portion will also be stressing the top portion of the fork, which on this bike has many stress risers formed into it (they are called threads for the headset). If the stem's wedge portion is within the threaded portion of the steerer, and not below the threads, the expansive forces from that wedge and the bending forces from so little insertion can and does damage/break off the top of the steerer. This is a much worse outcome when going down that hill. And it tends to be more expensive to replace the fork and stem than just the stem (and not including any injuries to you).

If you do replace the stem make sure the clamping diameters of the handle bars and that stem match. Andy