"Upon leaving a covenant, even with the Oswald method, half of the progress the player has made in ranking up in the covenant is lost, should they wish to rejoin later. For example, a rank requiring 20 humanity will be reduced to 10 if one should rejoin and want to attain the previously held rank."
Does this penalty still apply once the highest rank has been achieved?
I ask because for some of the Covenants there seems to be no benefit in attaining Rank 3. I was wondering if the benefit might be that this penalty no longer applies, thus you can always leave and return to that Covenant and retain all the benefits you had before.
Look at Chaos Servant - +3 gives nothing. As +2 requires only 30 Humaity one could donate 61 Humanity and still leave and come back and keep the benefits. I can't think what other purpose the additional 50 Humaity needed to get to 80 Humanity would have, except to guarantee one's +2 forever.