My thing is...not only is IFS just plainly unfalsifiable (I mean, how are we supposed to study these "parts?"), but even if one isn't bothered by the non-empirical nature of it (I am bothered, for the record, but even if one is not) why would someone want to reinforce feelings of multiplicity? Wouldn't the goal of trauma therapy not be to promote feelings of integrated identity and sense of self, rather than further reinforce feelings of instability? I would imagine there could be really unfortunate results if this were used on people with BPD or BPD-like traits. Also, interestingly enough, IFS was the modus operandi of the Castlewood Institute, which most here will know was notorious for accepting patients with severe eating disorders as inpatients, only for many of those same patients to end up diagnosed with DID and full of confabulated memories of early childhood abuse. The institute was sued into oblivion and now either doesn't exist or has been rebranded enough to shed its reputation.