rank 0: kicks a person out of the clan (his faction app will still stand, so u also have to click "Decline" on that one after this)
rank 1-4: basic membership, no management rights.
rank 5-9: manager, u can accept peoples faction apps, fix battle rosters/briefings, send merc money even though its not from your battle (this only works with defence battles though, to avoid merc pay abuse).
rank 9: your nick shows as being a "Diplomat" in the crpg page when u look up strat factions.
rank 10: manager + total control over peoples ranks, faction color and is also needed if u want to transfer your fief without doing an attack.