Layer selection tool is a great thing and speed up work a lot but there is a problem with accidentally selecting wrong layer. I have two suggestion how to minimize this problem: 1) Add a setting "ignore opacity less than X %" where X set by user. This will "fix" annoying situations when there is some not completely erased pixels from layer above. 2) Add a checkbox "ignored by layer selector" to layer properties (I think layer properties is the best place). So artist will can disable selecting layers that is not supposed to be selected, like sketch layer, overlay\multiply\color dodge layers, just layer that "finished", etc.
I noticed that locking layer also lock it from selection so p2 is technically already here. P1 still would be nice to have.
A popup with a list of layers to choose from in case of ambiguity would work IMO.
It's not really a tool, so there will be a problem where to put the setting. Also I'm not sure if comment 2 describes a proper behaviour... There is also a shortcut that selects *all* layers that result in a specific pixel.