My Venus Flytrap is quite crowded, there are traps under traps and I've noticed one clamped over the stems of another.
Should I prune it? Will it digest itself?
It won't digest live plant matter. Venus flytraps secrete the enzymes phosphatase, proteinase, nuclease and amylase. These enzymes target insect prey, which have high levels of protein. They do not digest plant matter. When a leaf closes on a bug, it (the bug) will often secrete chemicals such as uric acid, which keep the leaf closed. Otherwise (such as if the leaf should close upon plant matter), the leaf should soon reopen. You don't generally prune a Dionaea, as that often promotes new growth which may not have properly formed traps on the leaf ends.