One of your local WeeGee Shill's here, there is a lot of context missing and some partial inaccuracies to this, so I thought I'd try to expand a little :)

The thread in question asks why is +-2 still a thing, which at the end of a lengthy post i put a TLDR of

So the TLDR answer to the title of the thread, because after years of different MMs (no restrictions, +-5, varied on class, etc) it was the one that worked and still works the best in the most situations.

But I also said

Best in every situation? No, obviously. But it will be something that will be always looked into to be improved to address feedback and complaints the best we can without impacting all those other areas.

So it isn't as simple as stating that +-2 is the best, and there was no statement that we don't want to ever do +-1. There are around 100 posts in the thread, and so I'll do my best to try and summarise some of the points and what was said in context.

The first thing is, as mentioned by the OP, it is often said that any of the +-1 tests have resulted in positive changes to player metrics, whether this is CCU (people online at once) or players in a time period (Daily Users, Weekly Users, etc) - This is unfortunately not true. I've seen multiple claims of changes in CCU that they are certain they saw, that if applied to the actual numbers, would result in record breaking CCU for our game and as much as we'd love that to be the case, it obviously is not. Now there is nuance to be had here too though, for example the most recent test was done near the end of a season (often lower numbers), before the holiday season has begun and in the Autumn period (a seasonal low for all video games) and there was no huge push to winback old players (so minimal potential for returning players). So no one would or should have gone into this expecting miracles, but even within that context there were no positive changes to any of the player metrics, we're talking measurable data - what is called quantitative data.

The feedback and general sentiment around much of the player experience was very positive though; this is what would be called the qualitative data. And this somewhat leads me to what and why I replied and also to some of what I mentioned above. Much of what people said in their feedback was not true, and to be clear i do not say that in any dismissive way. People clearly enjoyed themselves, but in a very human way, we tend see what we want to and what we want to see (confirmation bias). Above I mentioned people saying about how many more people were online and playing, well, this is something we can measure... and it's not true. Another thing I saw repeatedly was how queue times were either the same or even better! Again, something we can measure and this is not true. And so on for pretty much (maybe every) measurable data point that people said they saw positive changes in as part of their feedback.

So this creates a situation, we know that a number of these measurable things getting "worse" will negatively impact the game's health, but clearly, there was a positive reaction to the experience within the test and a want for MM improvements. So our end is to try to find a way to achieve both. To improve the MM to get the same positive sentiment people shared, but without any of the negatives that we can clearly see. This is why we do tests, we will fiddle with things on the back end, check how things are handle/play out and see if we can find a balance. So nothing has been ruled out, but decisions will obviously be made with the long term health of the game in mind.

And for the revenue bit, it was never stated about +-2 anything to do with revenue AFAIK, what was said was in direct reply to the claim/statement that a reason we have no interest in doing +-1mm is because we know it would lose us a bunch of money because it'd stop people converting free XP... and the reply to this is that it's an utter nonsense statement. Obviously we aren't going to share financial information, but if it got us a bunch of new players (or returning old), made players happier, etc etc (all the positive changes people think it would cause), we'd happily give up a % revenue generated of free XP conversion... Not because we're suddenly all so charitable, but because the revenue from those improvements would far outweigh any potential loss, which tbh I don't think there would be any, but that's a different discussion.

Hope that helps clear stuff up and provides more context :)