Originally Posted by
akropilot
The main stress-riser you have to look out for is from the base of the stem causing wear on the steerer, or over-tightening causing shear/crushing of the steerer. In both cases it should show up as marks/cracks around the stem rather than longitudinal.
You can see an horizontal mark on the first picture, which was indeed caused by the bottom of the steerer. Inspection by LBS revealed it is within what's normal. Just to make sure, I have since changed my stem to one with more progressive edges and a greater contact area. Also installed a Specialized expander plug and nothing moved, so I guess all the vertical lines are normal (I know for sure the one with the blue arrow is, the one with the red arrow looked more weird because of the jagged pattern but it is really fine to the touch inside and out and doesn't produce a different sound when tapped)