I believe that the ultimate impact of this change is not well understood. That the potential breakage poses some risk to Rust’s reputation. I have until this point though not objected strenuously, hoping that this time it will turn out ok. So I think it would be unfair of me to do so now.
It may be that the mitigations in place are sufficient. That whatever rendering differences remain will be few, and we will receive few complaints. I don’t know. It seems likely to me that some people will see differences in their rendering, some people will file bugs and be angry, and then it will blow over, perhaps becoming a minor black mark on Rust’s history that people occasionally dredge up to point out that the Rust team doesn’t always make decisions consistent with their stated stability goals. It will almost certainly not be a major catastrophe.
If it were my call I would revert it and go back to hoedown, come up with a plan to better understand the impact, and better inform users about impending breakage. That though is much more work than just letting it go, and I am not the one to do that work.