under what circumstances does deleting files fail on a full pool? i have one that fills up semiregularly and i've never had issues that required me to truncate files
Any Copy-on-Write filesystem can run into this. There's always some way around it, but it can be problematic if you only have one device, can't remember the steps to fix a full filesystem, and can't look up the steps because you can't launch a browser without it trying to make some files!