"The rules don’t account for every possible situation that might arise during a typical D&D session."
When the game admits, in its introduction to the GM, that there's not a rule for everything, saying, "That's a house rule," does not give your argument much weight.
In case you didn't catch that part of the thread, I brought up, and linked, the exact Sage Advice you did. Oofta dismissed the idea that metal armor could be allowed by DM fiat as a house rule, nothing official, even though the SA outright said that it was a taboo, not a mechanical prohibition. So...?
Yes, I know "they started it" is not a good argument, either, but I feel rather singled out here when others have done the exact same thing but they're ignored.
If you really wanna keep beating your heads against each other in the face of what is, for once, some pretty solid advice about running and playing the game... well, there's 70 pages here of that already, isn't there? You think more will be better?
There's lots of great space to talk about cool reasons for why Druids might stick to this. And things they can do instead of metal armor. Maybe that's better then this IS RULE/IS NOT RULE thing.
There actually
has been discussion reasons why druids stick to not wearing metal armor, and those reasons seem to mostly amount to "tradition" and "it doesn't look right for druids to be wearing metal." Which is also one of the reasons why I've asked "what happens to a druid who wears armor," because there's neither lore nor mechanics about it in this edition.
Likewise, it's been brought up by several people, including myself, things that can be used in place of metal, like ironwood, chitin, I think petrified mushrooms... I even mentioned shellacked paper, as per
Chinese armor. Sadly, none of those materials are in the actual rules, and most of the time when they're brought in to the game, they're assumed to be some sort of magical armor, like dragonscale, which makes it difficult to actually obtain in game and prohibitively expensive for a druid to buy.
And when those materials have been brought up, those posts have mostly been ignored. Since some people are trying to claim that the only reason for people to want druids to wear some of the metal armors is for badwrongfun powergaming purposes, I feel that they are also ignoring these materials for the exact same reason. As if they've decided that all druids should only wear dead animals and be played in very traditional ways, even though many of the archetypes go very much against that tradition.