If my memory serves me right, then the commandment makes the user immune to the action of other Commandments. Accordingly, it is logical to assume that this effect from the two Commandments will make the user immune to the effect of both. After all, by default, everyone is susceptible to the effects of commandments, respectively, it only gives resistance from all commandments, except for its own, and does not make the user vulnerable to the action of a particular commandment.
I considered that, but I concluded that the vulnerability to the curses would probably take precedence over the immunity. This is because some of the curses seemed to have been designed with specific members of the Ten Commandment in mind. Monspeet's Commandment prevents people from expressing their hidden feelings, which is only a problem for those that have hidden feelings in the first place, such as Monspeet. Someone like Galand presumably wouldn't have suffered any drawbacks from that. He was instead given a curse that targets those that lie or go back on their word, which is very dangerous for a boastful moron like him. Meliodas, who displayed his greatest feats of strength when angry, was given a Commandment that weakens him if he feels hatred. Zeldris was made to be unable to go against the Demon King, even though he didn't care about his father's plans and just wanted to be with Gelda. If the Demon King went out of his way to give some of his elites the specific Commandments that would be the most difficult for them to follow, then it would be counterproductive if they could weasel their way out of following those rules just by obtaining more of them. Even just having two at once would cause them to negate each other along with all the others. It would therefore make more sense to me that anyone in possession of multiple Commandments would have to follow all of them.
The revel about the first Holy War was that it was the goddesses were the ones to start it, and their actions were what led the demons being as hostile as they were. After that point, the demons weren't shown as destructive before, and the whole soul devouring never came back up except with Estarossa. By the end of the series, I would say the Demon King was the only non-sympathetic named demon left, since aside from the ones who had already died, the rest were given backstories to justify their actions.
The goddesses were the ones who triggered the holy war by drawing all the other clans into it, but the conflict between the demons and goddesses was just something they did. This was elaborated on by the SD in the movie. Considering that humans, fairies and giants all agreed that the demons had to go, the demons must have been pretty nasty towards them as well.
Don't know how to argue with that, since it appears that the manga and the movie are contradicting each other. Unless the underground had the majority of people, Merlin not knowing about them shouldn't affect her statement. And I presumed there were still demons around due to the whole situation with the Coffin. Just Meliodas could explain that, but that seems overkill.
It's not necessarily a contradiction, it just depends on how the numbers work out. Merlin said that they had managed to evacuate most of the citizens, not including those hiding underground. If you take the people they failed to save, combine those with all the people underground and then factor in the people who died in battle when the demons first conquered Camelot, you could very well end up with quite a large body count. I'd say it's totally possible that Meliodas was the only target of the COED given that he's one of the strongest people in the world and has previously demonstrated that he is capable of injuring or even killing gods. I don't know how much of a threat he would pose to Arthur, but at the very least he has the power to wipe out all of the Chaos Knights in one attack. It makes sense that Ironside would be very concerned about him. Alternatively, it's possible that triggering the COED wouldn't just affect Britannia, but also the Demon Realm and all the demons living there.
They weren't there during the planning or when the fighting began, or when Estarossa and Derieri showed up, so they must have joined pretty late in the war. Regardless, they weren't there when the Holy War was named, which was my point. And according to Talisker, even helping the other races was considered a major sin, and he intended for Ordo to destroy them, but monster Ordo was still lenient towards them. It definitely seems as if they have an equal hatred toward all the other races.
Their forces were mentioned in chapter 257 when the battle plan was first laid out. It was Ludociel who informed everyone of this, so I think it's likely that he always intended to have them join the battle. It's possible that he had even contacted them before he arrived in Liones, because the giants and fairies both lived about 100 miles away and could still mobilize their forces and travel to the battlefield in about a day or so. As for Talisker, he says that he initially just advised Ordo to stop helping the fairies and giants. It was only after Ordo refused that Talisker turned him into a monster, but even then he just wanted Ordo to "raze the land" instead of killing all the non-humans. That seems to me like a more peaceful approach than Ardbeg spending who knows how long trying to wipe out the demon village, or Ironside being willing to sacrifice an entire human town to trigger the COED. Talisker didn't behave as if the fairies and giants had been involved in slaughtering his countrymen and destroying his kingdom.
Well I presume that Camelot wasn't destroyed the second time, that's just the belief due to it being gone. That would explain how it could both have fallen and still be around as we're told. As for Meliodas being the leader, it can easily not be meant as literal - Ironside's comments to the people of Sistana proclaimed that Liones was evil, and that they were gathering the Four Knights of the Apocalypse, "dreadful demons" according to him, to destroy the world. So we were shown Arthur's knights don't have an issue with claiming they're opposing demons when they're really not. We know that it's not merely the Sins, but Liones itself that is considered Camelot's largest opposing force according to Arthur. Gowther also stated that the Sins were the sworn enemies of Arthur. Add in Tristan working as an agent of Liones, and it would be really strange if there hadn't be some major conflict between the two kingdoms to establish their need to both build forces against each other.
I suppose Camelot's supposed destruction could be explained as Arthur teleporting it away or something, but that doesn't address the deaths of his countrymen. Why would so few of them survive the destruction of Camelot, if what actually happened was the kingdom just being moved? What's more, your theory is that this happened in a fight against the Sins, and I don't see why they would kill a bunch of civilians, especially after going out of their way to save them earlier. I doubt Arthur would do something that endangered his people either, given that the trauma of losing them seems to have contributed towards him wanting to get rid of the other clans. I think it makes more sense to assume that Arthur never rebuilt Camelot in Britannia to begin with, and opted to just construct a giant graveyard in its place while secretly constructing the everlasting kingdom in an entirely separate realm. This sequence of events doesn't mean that the Sins couldn't have confronted Arthur at some point, but I highly doubt that it would have been some sort of a massive battle that killed a bunch of people and potentially wiped out the kingdom again. This is supported by how Ironside doesn't seem to know just how powerful the Sins truly are, since he thought destroying some house monsters would put someone on their level. Some sort of a smaller skirmish makes more sense to me, but even that's not really necessary for the two parties to consider each other as enemies seeing how their values are in direct opposition to one another. The conflict between Camelot and Liones could be as simple as Arthur's knights going around terrorizing non-humans, and Liones responding by sending their knights to put a stop to it.
You mention Ironside lying about Meliodas' role, which wouldn't be too surprising given that he seems to be full of lies, but the problem is that it wasn't Ironside, but Donny who said Camelot was wiped out by the leader of the demons. You could argue that he was affected by propaganda, but Donny is a student and close relative of Howzer's, the captain of Liones' knights and someone who actually participated in the Holy War. I very much doubt that Donny would want anything to do with Liones if he believed that they were evil kingdom destroyers, or that Howzer would never correct him about it. It would be yet another situation where characters have differing accounts of the events but somehow nobody realizes this even when the characters discuss these events.
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