10+ years ago I had a job which involved developing/testing geo-restricted software in another country. Eventually each VPN exit point would get marked up as such, and I would have to switch to another.
So if posts were marked with the country of origin or VPN, that might be enough for most people to evaluate the intent of the post.
Of course things have changed. There might not be so many IPv4 addresses around to trade, but IPv6 has probably changed that. And it's probably hard to know how long an address was used by a VPN before being traded back to a telco.
I think Russia did, successfully for quite some time, attempt to direct anger towards the countries supporting Ukraine. Russia would drop a bomb on Ukraine and 90% of the comment section would hate the West for it. The goal was to fuel defeatism and infighting. The latter they encouraged from the start. Reading Reddit, you would have thought Germany had attacked Ukraine from the western flank. In the days and weeks before every major pending Ukraine decision in the US, you could see a noticeable uptick of Russian-friendly talking points. Before the US election, a suspicious amount of Redditors claimed that Trump would give Ukraine more weapons than Biden. These days, they are encouraging the Europe is weak rhetoric. If a toy drone gets spotted somewhere, the only acceptable response is nuking Moscow and EU should disband if they don't dare - that inane take to me is also trolling.
There is no incentive to implement such a feature. Bots and paid social media workers drive engagement. Also social media sites are designed to avoid any triggers that make users click away (like showing origin flags that would allow a user to easily dismiss a thread as fake). This is the same reason why Youtube removed dislike counts.
Man if Russia went dark like half of all politics X and Reddit would probably go dark. I bet it would be both ends of the horseshoe.