I had a stripped one of those and a helicoil later it was sorted. Fortunately I had the head off at the time and went through and fixed all the threads. I spose it wouldn't be the end of the world to pull the timing cover to fix it.
seen quite a few of them stripped, often thought of grinding the edge of a 6mm nut and fitting it to a longer bolt (can see the tip of the bolt behind p/s pump) but the idea never went further than a thought!