While not absolutely positive... you could test your own questions by doing negative things and see if you generate negative rapport by doing them. Since it appears you know how to raise rapport, doing a few negative things to see if they impact rapport would be easy to test.

My thoughts... yes, once you hit max, it is still absolutely possible to generate negative rapport. It wouldn't make sense for the rapport system to stop just because you hit max positive rapport. It's a sliding scale. So just like in real life, you may have the perfect friendship, but you may do something negative which could seriously jeopardize your RL friendship. I think this is how ZOS designed it... so that rapport is give and take.

So that answers your second question... do enough negative actions and yes, your rapport could definitely dip below ally.

Third... a momento is never taken away... it's an 'achievement' for reaching that unlock level.

Jacozilla wrote: »

So basically then, there is zero negatives to doing whatever you want, e.g steal kill etc after maxing out your companions rapport and getting the memento, because if that unlock is permanent, then long as companion is still summonable there is no downsides to reducing your rapport via negative actions

I am not willing to test it but I can’t see how a companion can ever become unsummonable due to low rapport. Because if you can’t summon them, then how could you repair your rapport with positive actions?

They don't become permanently unsummonable. It's only "for some time." I don't think anyone's been dedicated enough to get low enough rapport to find out what the cooldown is.

So I can actually confirm that this seems to be bugged atm and once you max out your rapport and attain "Companion" rank it can no longer go down regardless of how many things you do that your companion disapproves of. I figured this out accidentally when I had Bastian out while dueling for the endeavor and killed an NPC that happened to walk into my ground AoE.

I proceeded to get a stern lecture from Bastian about how killing innocents would fracture my soul and received the notification for lost rapport. Same thing happened a second later when I used a pardon item which apparently he also disapproves of. And then yet again when I went to craft something with cheese for the daily writ which his lactose intolerant a$$ also hates, lmao. So at that point it got annoyed and went ahead and completed the remaining two endeavors for pickpocketing and murdering citizens with the Blade of Woe without dismissing him like I normally do. Tons and tons of notifications popped up again as you can imagine accompanied by the audio cues of disapproval he gives, however, the rapport bar did not budge at all nor did the rank change.

If after that kind of a murderous and thieving rampage, to say nothing of my use of the dreaded cheese, there were no consequences I have to conclude it's either bugged or working as intended and it's just not possible to lose rapport after its been maxed out which goes contrary to what they have said but there you have it.