IMHO, it also depends on the frame. If we're talking a conventional tube constructed frame, if the bottom of the post is below the bottom of the top tube, you're likely ok. I rode a steel frame where the minimum insertion mark was just exposed above the frame lug, half the way around ( the lug was curved) for years with no adverse effect.

If the seat tube on your frame sticks up above the top tube, so that you're not getting the seatpost below the top tube, I wouldn't do it. If the seat post still reaches below the tt, you're likely ok.

Realize that the minimum inseertion mark is put on the post to deal with a range of frames. What you actually need for your seatpost, frame interface can varie.

All that said a longer seatpost is cheap.