Commonly misunderstood rules

[TheUser]

Yeah, the wording on some of these are... strange. But all of them can be easily fixed with a dose of common sense.

My point is that the rules should just work. "Common sense" isn't quite as common as you might think...Like now I have to explain how words work...which I thought was common sense.

Wall of Fire: This one's confusing but it's all there. You don't take damage from the "hot" side if you're inside the wall, so only one 5d8 roll. Unless I'm missing what you mean there.

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One side of the wall, selected by you when you cast this spell, deals 5d8 fire damage to each creature that ends its turn within 10 feet of that side or inside the wall. A creature takes the same damage when it enters the wall for the first time on a turn or ends its turn there. The other side of the wall deals no damage.
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Pretty cut and dry. You end inside the 1ft thick wall you take 5d8 twice. Makes sense thematically too; the wall would be hotter inside than 5ft away.

Inured to Undeath: The rule is your max HP can't be reduced, but temp HP don't increase your max HP. They just stack on top. This is more a problem of understanding temp HP than this feature.

I am afraid it is you who is misunderstanding as you have misread what I wrote. I wrote temporary maximum HP boost (think the aid spell) not temporary HP. Common sense amiright?
The interaction, to be explicit, is that when the aid spell ends it is technically reducing your max HP and so Inured kicks in and says "can't be reduced" and you now have a permanent boost to your max HP.