I think you may be exaggerating slightly the peculiarities of legal English.  The normal phrasing is, for example "This complaint is about a folder, *which folder* went missing on Tuesday last..."  So *which* is natural and normal; it's *folder* that is unnecessary padding/zealous for clarity, as you prefer.  The difference from your example is the difference between 'the folder which went missing' and 'the folder, which went missing,' ; minute, but possibly important.