I have come across "order was received from General Allenby" (or something similar) in the diary I am tagging. There was no appropriate tag under "Person" for "Orders received from" or "Gave orders". I just had to select "other" which seemed a bit non-discript.
While Other may seem a bit vague, if the project went into that level of detail for everyone involved in the war the options list would be too long to be useable. I think the intention is to tag people's names so that they can later be easily found in the diaries and only record details of events affecting him (casulty, medals or promotion) or the unit (transferred out, joined).