Thanks for the comments, everyone!
Thanks! I found that thread when I was first looking for tips on how to draw mountains, and tried to follow some of the principles people explained there... although I couldn't find it again when I came to post this, possibly because I was looking in the wrong place.
That is intentional - the idea being to distinguish the shadows on the mountain slopes from the shadow they cast on the ground behind - although I'm inclined to agree that it doesn't really work.
The two smaller ranges on the right are those that gave me most trouble. It's handy in a way that these ranges (which are for a particular map) give a variety of angles to depict as each seems to present fresh issues.
In the upper left, this was also something which gave me problems. Assuming the light is coming from the right of the image, if the reverse slopes were shown it made it look as if the whole left slope of the mountain should be in shadow, which made them very dark considering not much of the reverse could be seen. On the other hand, not showing the reverse slope makes the mountain look strange and a bit 2D as you say. It obviously works better in the lower right where the the side most visible is the one directly in the light.
I think I see the pointy one you mean; I'm not sure what happened there. I think for some reason I naturally want to finish things off at a steep angle, as I found when drawing some fresh ones and despite bearing it in mind finding my pen curving downwards at the end of each stroke...
Anyway, I've tried re-drawing the range, with shading still to be added.
This is roughly where it looks to me like the shading should go, but I'm not entirely sure. In the upper left I've tried two different placings: one as in the first version, and one with the whole "near side" shaded. The second probably looks more accurate but I'm concerned that it will make the whole image very dark.