Initially I was ready to facepalm. All I could think about was tanks like the Defender, Chrysler, Minuteman, Absolution, V/IV etc never having to face tanks two tiers higher, and how it was a buff for them. I also thought this was a poor substitute for proper tank balancing and honestly, a bit lazy. I also worried about tier 9. They are going to be dragged into tier 10 games ALOT now no doubt, so tier 9 stock grinds are going to hurt. However, then I thought about it a bit more and found some positives.
Whilst the premium tanks I listed above don't face tanks two tier above them this week, the tanks that couldn't really hurt them reliably, those tier 2s below them, were now safe from them. This fact alone instantly makes tanks that were powercreeped now a bit more viable again.
A few OP tanks get an indirect buff, but so do alot of very average tanks. Albeit the stock tier 9s suffer for it. Then I played a few games. More people were getting stuck in, people were saying on game chat how nice it was for them for the game to be a bit more of an even playing field tank wise too. The change had made the game a bit easier for them and less daunting. As these players make up the vast majority of the player base, this is good.
A mate pointed out another downside but it will only consistently affect blues, purples and super purples, and that is, with not facing tanks 2 tiers higher, there isn't as much damage to farm in game.
I also think PMM tanks should, as I've also seen others suggest, get to have - 1/0 MM.
In general, whilst it certainly does have flaws, I think the positives are worth the negatives and hope to see it become more permanent. There are OP tanks that benefit alot from it, but it is obvious WG wont nerf them anytime soon and at least the tanks 2 tiers down are safe from them this way.
P. S the Jackal is hilarious with this MM.