Chaosmancer
Legend
I would have a snappy answer to this failure at debunking but the following is right there
And to go a bit further.
You have to apply correctly this: "consider the deity's suggested domains when selecting your character's domain."
This is not to say that you can ignore the suggested domains. It means to pick one of the suggested domain that will most suit your character. I am starting to believe that you read not the words, but what you want to read. Yes, stretching the meaning could be done. But it fails any close scrutini.
The actual read is reinforced with this quote: "Alternatively, your choice of domain could simply be a matter of personal preference, the aspect of the deity that appeals to you most." So the domain chosen must represent the deity at some point. And guess what? They provided some with the appendix and in the DMG.
In the DMG, it is even suggested that if you want to create your own pantheons jyou just have to pick one domain and assigned each one to a single god. This says a lot in itself. A god can be tied to only one domain and all clerics of that domain will belong to that god! Allowing two or three choices just make a god more powerful and more appealing to a wider variety of worshippers.
In fact, only in the monotheistic part, domains are clearly an open choice. But even then, it is an aspect of the One God that you will choose to worship/champion. In real world therms, you are Jesuite, a Templar, a Trappist or a member of some order of the One God. But all members of these orders are taking the same domain... On that, good night. Have to work tomorrow.
And this is pretty trivially easy to disprove.
Let us look to Tasha's. There we see the Twilight Domain cleric. This cleric is associated with the stars, and night, but also watchfulness and vigilance. We know that protection and vigilance are part of the Twilight Domain, because one of the Gods associated with the Twilight Domain is Helm, God of Watchers.
Now, Tasha's was released AFTER Mordenkainens, so all the gods in Mordenkainen's would be fair game to be mentioned in Tasha's, correct? And we know that Tasha's lists can include racial deities because the Twilight includes Yondalla the Halfling Goddess.
Who does it not include?
Angharradh - Elf God of Protection
Araleth Letheranil - Elf God of Stars
Vandria Gilmadrith - Elf God of Vigilance
Gorm Gulthyn - Dwarf God of Vigilance
Arvoreen - Halfling Goddess of Vigilance
Gaerdal Ironhand - Gnomish Goddess of Protection
I could even include the Deities of Community, because another listed Deity of the Twilight Domain is Boldrei, the Eberron Goddess of Community. But, it was shorter to just list the deties of protection. So, either Helm should not have been listed with the Twilight Domain, or all of these deities should have been listed with the Twilight domain.
Third option? The domains are suggestions and can be chosen and applied to any deity it makes sense to apply them to.