I do wonder though whether this change would be reverted or not if the naysayers end up being mostly right in the future.
I wonder how an outcome could look where the "naysayers end up being mostly right". I guess you refer to a possible wave of spam via big OP_RETURN data transactions.
But is this a realistic outcome? We have to take into account that the limits increase does not create additional incentives for data transactions, because there are already cheaper options like the Taproot "exploit". And the Bitcoin Stamps method is almost as cheap as the OP_RETURN method (but much more harmful to nodes resources).
I am not debating whether it is a realistic outcome. There are only two cases here: Either the counterarguments are valid concerns, or they are not valid concerns. If they are valid, then there’s a chance the consequences mentioned could come to fruition, right? What I am wondering is, if things do happen in a way that proves the naysayers partially or fully right, would Core undo these changes or would they find
reasons excuses to not do it. That would provide a very clarifying situation for the reality of social power dynamics here, much better than any theoretical debate that we could have on this topic.
Then all what's left for such an outcome is a "social" effect, i.e. some people could think that "Bitcoin" now "approves" the usage as a data storage and thus are more comfortable using tokens or NFTs based on OP_RETURN.
I guess however this would be an extremely weak effect. Because the big "spam" waves like Ordinals Inscriptions benefitted from scarcity. If you created a big NFT paying a lot of fees to a miner to mine a non-standard transaction, then if this type of transaction became "standard", this would lower the scarcity and thus the price of the NFT.
An example: A couple of pages ago a new OP_RETURN based "non standard token" protocol was mentioned. The "scarcity" of these tokens due to their non-standardness (and thus the potential re-selling value) was one of the promised "features". However, with OP_RETURN limits lifted, this would mean that many nodes could treat these tokens as "standard" and thus it would be easier to create them. In the long run this would lead to less of these transactions, because they still cost fees but lack any "scarcity".
I could also imagine a "vengeance spam wave" from those opposing this PR. This would however probably be a short term effect.
The rest of this is very well written, and I like that you described some possibilities. For that, I leave you some merit. I think a lot has been said about potential consequences everywhere where this was discussed, and because I don't want to continue this particular subtopic further I'll leave it at that. Now that it has
been merged, we will soon see what will really happen.

It looks like the subject was brought up again with a different approach, but I'm not smart enough to understand how its different or the implication of the 5 commits being merged as of 2 days ago:
As pointed out up-thread: it was closed in favor of an alternative approach that kept the setting but changed the default.
You might have also missed that in the middle the project published a statement clarifying its approach to the default policy behavior for relay:
https://bitcoincore.org/en/2025/06/06/relay-statement/ Why are there some conspicuously missing names from that list?
It is a bit short for me as well, but I guess more context is needed to know why.
it's almost always been the case that working on alternatives would pay a lot more and so people who have worked extensively on Bitcoin have done so out of principle.
I didn't know that, to be honest. I thought core devs received enough donations to make working on other projects a lot less tempting. Obviously, this kind of information isn't public, so we have to take your word for it -- and I don't see any reason to deny it.
I am surprised that you don't know this. Just look at how much money altcoin projects are raising for absolute vaporware garbage that nobody needs. Hundreds of millions of dollars. Core developers could probably earn a lot of money by just giving permission to be listed as advisors in a variety of project. Just imagine the money if they participated in some more deeply, as co-founders. Integrity is what keeps them away. People have left for very different reasons, and some have shown their true colors with the act of leaving. You mention some very bad examples. In the case of mr. Hearn, he wanted to control Bitcoin and turn it into a centralized nightmare. When his proposals got rejected, he slowly went away and joined the "enemy". 